[feat] add OpenGL NV12 underlay rendering for Slint on Linux

src/gui/application/gui_application.cpp

@@ -36,7 +36,6 @@
 #include <GL/gl.h>
 
 #include "platform/tray/win_tray.h"
-#include "platform/windows_opengl_video_renderer.h"
 #elif defined(__APPLE__)
 #include "platform/metal_video_renderer.h"
 #include "platform/tray/mac_tray.h"
@@ -49,6 +48,9 @@
 
 #include "platform/tray/linux_tray.h"
 #endif
+#if defined(_WIN32) || defined(__linux__)
+#include "platform/opengl_video_renderer.h"
+#endif
 #include "rd_log.h"
 #include "server_window_state.h"
 #include "ui/ui_localization.h"
@@ -62,6 +64,7 @@ using namespace std::chrono_literals;
 
 #if !defined(__APPLE__)
 constexpr GLint kGlClampToEdge = 0x812F;
+constexpr float kStreamWindowCornerRadius = 12.0f;
 #else
 constexpr int kMetalAttachmentAttemptLimit = 30;
 #endif
@@ -1114,9 +1117,8 @@ void GuiApplication::InitializeModules() {
   if (modules_inited_) {
     return;
   }
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-  windows_opengl_video_renderer_ =
+  opengl_video_renderer_ = std::make_unique<OpenGlVideoRenderer>();
-      std::make_unique<WindowsOpenGlVideoRenderer>();
 #elif defined(__APPLE__)
   // Metal setup can log device, shader, or pipeline failures. Initialize it
   // here, after Run() has selected the application's log directory, rather
@@ -2351,9 +2353,9 @@ void GuiApplication::SyncStreamWindow() {
   }
   if (!has_sessions) {
     SetStreamKeyboardFocus(false);
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-    if (windows_opengl_video_renderer_) {
+    if (opengl_video_renderer_) {
-      windows_opengl_video_renderer_->SetSelectedStream({});
+      opengl_video_renderer_->SetSelectedStream({});
     }
 #endif
 #if defined(__APPLE__)
@@ -2643,10 +2645,10 @@ void GuiApplication::SyncStreamVideoFrame() {
   }
 #endif
 
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-  if (windows_opengl_video_renderer_ &&
+  if (opengl_video_renderer_ &&
-      windows_opengl_video_renderer_->IsReady()) {
+      opengl_video_renderer_->IsReady()) {
-    windows_opengl_video_renderer_->SetSelectedStream(props->remote_id_);
+    opengl_video_renderer_->SetSelectedStream(props->remote_id_);
     SubmitCachedFrameToOpenGl(props);
     if (!(*ui_->stream)->get_native_video_enabled()) {
       (*ui_->stream)->set_native_video_enabled(true);
@@ -2854,10 +2856,10 @@ void GuiApplication::ConfigureStreamVideoRenderer() {
           glBindTexture(GL_TEXTURE_2D,
                         static_cast<GLuint>(previous_texture));
           ui_->video_gl_texture = texture;
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-          if (windows_opengl_video_renderer_ &&
+          if (opengl_video_renderer_ &&
-              windows_opengl_video_renderer_->Setup()) {
+              opengl_video_renderer_->Setup()) {
-            windows_opengl_video_renderer_->SetSelectedStream(
+            opengl_video_renderer_->SetSelectedStream(
                 focused_remote_id_);
             video_frame_dirty_.store(true, std::memory_order_release);
           }
@@ -2865,10 +2867,10 @@ void GuiApplication::ConfigureStreamVideoRenderer() {
           return;
         }
 
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
         if (state == slint::RenderingState::BeforeRendering &&
-            windows_opengl_video_renderer_ &&
+            opengl_video_renderer_ &&
-            windows_opengl_video_renderer_->IsReady() && ui_->stream &&
+            opengl_video_renderer_->IsReady() && ui_->stream &&
             (*ui_->stream)->get_native_video_enabled()) {
           const auto window_size = (*ui_->stream)->window().size();
           const float scale_factor =
@@ -2877,9 +2879,18 @@ void GuiApplication::ConfigureStreamVideoRenderer() {
               !fullscreen_button_pressed_ && ui_->tab_ids.size() > 1
                   ? static_cast<int>(std::lround(30.0f * scale_factor))
                   : 0;
-          windows_opengl_video_renderer_->RenderLatest(
+          const bool rounded_window =
+              (*ui_->stream)->get_custom_titlebar() &&
+              !fullscreen_button_pressed_ &&
+              !(*ui_->stream)->window().is_maximized();
+          const int corner_radius =
+              rounded_window
+                  ? static_cast<int>(std::lround(
+                        kStreamWindowCornerRadius * scale_factor))
+                  : 0;
+          opengl_video_renderer_->RenderLatest(
               focused_remote_id_, static_cast<int>(window_size.width),
-              static_cast<int>(window_size.height), top_inset);
+              static_cast<int>(window_size.height), top_inset, corner_radius);
           return;
         }
 #endif
@@ -2914,9 +2925,9 @@ void GuiApplication::ConfigureStreamVideoRenderer() {
         }
 
         if (state == slint::RenderingState::RenderingTeardown) {
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-          if (windows_opengl_video_renderer_) {
+          if (opengl_video_renderer_) {
-            windows_opengl_video_renderer_->Teardown();
+            opengl_video_renderer_->Teardown();
           }
 #endif
           if (ui_->video_gl_texture != 0) {
@@ -2933,19 +2944,19 @@ void GuiApplication::ConfigureStreamVideoRenderer() {
       });
   if (error.has_value()) {
     LOG_WARN("Slint OpenGL video renderer unavailable, using pixel buffers");
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-  } else if (windows_opengl_video_renderer_) {
+  } else if (opengl_video_renderer_) {
-    windows_opengl_video_renderer_->SetSelectedStream(focused_remote_id_);
+    opengl_video_renderer_->SetSelectedStream(focused_remote_id_);
 #endif
   }
 #endif
 }
 
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
 void GuiApplication::SubmitCachedFrameToOpenGl(
     const std::shared_ptr<RemoteSession>& session) {
-  if (!session || !windows_opengl_video_renderer_ ||
+  if (!session || !opengl_video_renderer_ ||
-      !windows_opengl_video_renderer_->IsReady() ||
+      !opengl_video_renderer_->IsReady() ||
       session->connection_status_.load() != ConnectionStatus::Connected) {
     return;
   }
@@ -2968,10 +2979,10 @@ void GuiApplication::SubmitCachedFrameToOpenGl(
   }
 
   if (cached_frame && cached_width > 0 && cached_height > 0 &&
-      windows_opengl_video_renderer_->SubmitCachedNv12(
+      opengl_video_renderer_->SubmitCachedNv12(
           session->remote_id_, cached_frame->data(), cached_frame->size(),
           cached_width, cached_height) ==
-          WindowsOpenGlVideoRenderer::SubmitResult::submitted) {
+          OpenGlVideoRenderer::SubmitResult::submitted) {
     video_frame_dirty_.store(true, std::memory_order_release);
   }
 }
@@ -3321,7 +3332,7 @@ void GuiApplication::SelectStreamTab(int index) {
     return;
   }
   const std::string selected_remote_id = ui_->tab_ids[index];
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
   const bool selection_changed = focused_remote_id_ != selected_remote_id;
   bool renderer_selection_changed = false;
 #endif
@@ -3331,10 +3342,10 @@ void GuiApplication::SelectStreamTab(int index) {
   }
   focused_remote_id_ = selected_remote_id;
   controlled_remote_id_ = selected_remote_id;
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-  if (windows_opengl_video_renderer_) {
+  if (opengl_video_renderer_) {
     renderer_selection_changed =
-        windows_opengl_video_renderer_->SetSelectedStream(selected_remote_id);
+        opengl_video_renderer_->SetSelectedStream(selected_remote_id);
   }
   if (renderer_selection_changed) {
     video_frame_dirty_.store(true, std::memory_order_release);
@@ -3371,7 +3382,7 @@ void GuiApplication::SelectStreamTab(int index) {
         selected_session->connection_status_.load() ==
             ConnectionStatus::Connected;
   }
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
   if (renderer_selection_changed) {
     SubmitCachedFrameToOpenGl(selected_session);
   }
@@ -3427,9 +3438,9 @@ void GuiApplication::CloseStreamTab(const std::string& remote_id) {
   if (focused_remote_id_ == remote_id) {
     focused_remote_id_.clear();
     controlled_remote_id_.clear();
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-    if (windows_opengl_video_renderer_ &&
+    if (opengl_video_renderer_ &&
-        windows_opengl_video_renderer_->SetSelectedStream({})) {
+        opengl_video_renderer_->SetSelectedStream({})) {
       video_frame_dirty_.store(true, std::memory_order_release);
     }
 #elif defined(__APPLE__)
@@ -3631,9 +3642,9 @@ void GuiApplication::Cleanup() {
   WaitForThumbnailSaveTasks();
   devices_.DestroyAudioOutput();
   if (ui_->stream) {
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-    if (windows_opengl_video_renderer_) {
+    if (opengl_video_renderer_) {
-      windows_opengl_video_renderer_->SetSelectedStream({});
+      opengl_video_renderer_->SetSelectedStream({});
     }
 #endif
 #if defined(__APPLE__)

src/gui/application/gui_application.h

@@ -41,7 +41,7 @@ private:
   void SyncStreamVideoFrame();
   void ScheduleNextVideoFrame();
   void ConfigureStreamVideoRenderer();
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
   void SubmitCachedFrameToOpenGl(
       const std::shared_ptr<RemoteSession>& session);
 #endif

src/gui/platform/opengl_video_renderer.cpp

@@ -1,13 +1,20 @@
-#include "platform/windows_opengl_video_renderer.h"
+#include "platform/opengl_video_renderer.h"
 
-#if !defined(_WIN32)
+#if !defined(_WIN32) && !defined(__linux__)
-#error "WindowsOpenGlVideoRenderer is only available on Windows"
+#error "OpenGlVideoRenderer is only available on Windows and Linux"
 #endif
 
+#if defined(_WIN32)
 #include <windows.h>
+#elif defined(__linux__)
+#include <dlfcn.h>
+#endif
 
 #include <GL/gl.h>
 #include <GL/glext.h>
+#if defined(__linux__)
+#include <GL/glx.h>
+#endif
 
 #include <algorithm>
 #include <array>
@@ -49,6 +56,7 @@ struct SharedFrameState {
 };
 
 template <typename T> bool LoadOpenGlFunction(T *function, const char *name) {
+#if defined(_WIN32)
   PROC address = wglGetProcAddress(name);
   if (address == nullptr || address == reinterpret_cast<PROC>(1) ||
       address == reinterpret_cast<PROC>(2) ||
@@ -58,6 +66,14 @@ template <typename T> bool LoadOpenGlFunction(T *function, const char *name) {
     address = module ? GetProcAddress(module, name) : nullptr;
   }
   *function = reinterpret_cast<T>(address);
+#elif defined(__linux__)
+  void *address = dlsym(RTLD_DEFAULT, name);
+  if (address == nullptr) {
+    address = reinterpret_cast<void *>(
+        glXGetProcAddressARB(reinterpret_cast<const GLubyte *>(name)));
+  }
+  *function = reinterpret_cast<T>(address);
+#endif
   return *function != nullptr;
 }
 
@@ -85,7 +101,10 @@ struct OpenGlFunctions {
   PFNGLGETVERTEXATTRIBPOINTERVPROC get_vertex_attrib_pointer_v = nullptr;
   PFNGLLINKPROGRAMPROC link_program = nullptr;
   PFNGLSHADERSOURCEPROC shader_source = nullptr;
+  PFNGLUNIFORM1FPROC uniform_1f = nullptr;
   PFNGLUNIFORM1IPROC uniform_1i = nullptr;
+  PFNGLUNIFORM2FPROC uniform_2f = nullptr;
+  PFNGLUNIFORM4FPROC uniform_4f = nullptr;
   PFNGLUSEPROGRAMPROC use_program = nullptr;
   PFNGLVERTEXATTRIBPOINTERPROC vertex_attrib_pointer = nullptr;
 
@@ -116,7 +135,10 @@ struct OpenGlFunctions {
                               "glGetVertexAttribPointerv") &&
            LoadOpenGlFunction(&link_program, "glLinkProgram") &&
            LoadOpenGlFunction(&shader_source, "glShaderSource") &&
+           LoadOpenGlFunction(&uniform_1f, "glUniform1f") &&
            LoadOpenGlFunction(&uniform_1i, "glUniform1i") &&
+           LoadOpenGlFunction(&uniform_2f, "glUniform2f") &&
+           LoadOpenGlFunction(&uniform_4f, "glUniform4f") &&
            LoadOpenGlFunction(&use_program, "glUseProgram") &&
            LoadOpenGlFunction(&vertex_attrib_pointer, "glVertexAttribPointer");
   }
@@ -205,7 +227,7 @@ void RestoreVertexAttrib(const OpenGlFunctions &gl, GLuint index,
 
 } // namespace
 
-struct WindowsOpenGlVideoRenderer::Impl {
+struct OpenGlVideoRenderer::Impl {
   OpenGlFunctions gl;
   std::shared_ptr<SharedFrameState> frames =
       std::make_shared<SharedFrameState>();
@@ -218,6 +240,10 @@ struct WindowsOpenGlVideoRenderer::Impl {
   GLint texcoord_location = -1;
   GLint y_texture_location = -1;
   GLint uv_texture_location = -1;
+  GLint target_size_location = -1;
+  GLint video_rect_location = -1;
+  GLint corner_radius_location = -1;
+  GLint video_enabled_location = -1;
   int texture_width = 0;
   int texture_height = 0;
   std::string uploaded_stream;
@@ -232,6 +258,10 @@ struct WindowsOpenGlVideoRenderer::Impl {
     texcoord_location = -1;
     y_texture_location = -1;
     uv_texture_location = -1;
+    target_size_location = -1;
+    video_rect_location = -1;
+    corner_radius_location = -1;
+    video_enabled_location = -1;
     texture_width = 0;
     texture_height = 0;
     uploaded_stream.clear();
@@ -239,12 +269,12 @@ struct WindowsOpenGlVideoRenderer::Impl {
   }
 };
 
-WindowsOpenGlVideoRenderer::WindowsOpenGlVideoRenderer()
+OpenGlVideoRenderer::OpenGlVideoRenderer()
     : impl_(std::make_unique<Impl>()) {}
 
-WindowsOpenGlVideoRenderer::~WindowsOpenGlVideoRenderer() = default;
+OpenGlVideoRenderer::~OpenGlVideoRenderer() = default;
 
-bool WindowsOpenGlVideoRenderer::Setup() {
+bool OpenGlVideoRenderer::Setup() {
   if (IsReady()) {
     return true;
   }
@@ -274,15 +304,41 @@ precision mediump float;
 #endif
 uniform sampler2D y_texture;
 uniform sampler2D uv_texture;
+uniform vec2 target_size;
+uniform vec4 video_rect;
+uniform float corner_radius;
+uniform float video_enabled;
 varying vec2 video_texcoord;
 void main() {
+  vec2 surface_point = video_texcoord * target_size;
+  vec3 rgb = vec3(0.0);
+  if (video_enabled > 0.5 &&
+      surface_point.x >= video_rect.x &&
+      surface_point.x <= video_rect.x + video_rect.z &&
+      surface_point.y >= video_rect.y &&
+      surface_point.y <= video_rect.y + video_rect.w) {
+    vec2 frame_texcoord =
+        (surface_point - video_rect.xy) / video_rect.zw;
     float y = 1.16438356 *
-            (texture2D(y_texture, video_texcoord).r - 16.0 / 255.0);
+              (texture2D(y_texture, frame_texcoord).r - 16.0 / 255.0);
-  vec2 uv = texture2D(uv_texture, video_texcoord).ra - vec2(0.5, 0.5);
+    vec2 uv =
-  vec3 rgb = vec3(y + 1.59602678 * uv.y,
+        texture2D(uv_texture, frame_texcoord).ra - vec2(0.5, 0.5);
+    rgb = clamp(vec3(y + 1.59602678 * uv.y,
                      y - 0.39176229 * uv.x - 0.81296764 * uv.y,
-                  y + 2.01723214 * uv.x);
+                     y + 2.01723214 * uv.x),
-  gl_FragColor = vec4(clamp(rgb, 0.0, 1.0), 1.0);
+                0.0, 1.0);
+  }
+  float coverage = 1.0;
+  if (corner_radius > 0.0) {
+    vec2 half_size = target_size * 0.5;
+    vec2 corner = abs(surface_point - half_size) -
+                  (half_size - vec2(corner_radius));
+    float distance_to_edge =
+        length(max(corner, vec2(0.0))) +
+        min(max(corner.x, corner.y), 0.0) - corner_radius;
+    coverage = clamp(0.5 - distance_to_edge, 0.0, 1.0);
+  }
+  gl_FragColor = vec4(rgb * coverage, coverage);
 }
 )glsl";
   static constexpr char kDesktopVertexShader[] = R"glsl(
@@ -299,15 +355,41 @@ void main() {
 #version 110
 uniform sampler2D y_texture;
 uniform sampler2D uv_texture;
+uniform vec2 target_size;
+uniform vec4 video_rect;
+uniform float corner_radius;
+uniform float video_enabled;
 varying vec2 video_texcoord;
 void main() {
+  vec2 surface_point = video_texcoord * target_size;
+  vec3 rgb = vec3(0.0);
+  if (video_enabled > 0.5 &&
+      surface_point.x >= video_rect.x &&
+      surface_point.x <= video_rect.x + video_rect.z &&
+      surface_point.y >= video_rect.y &&
+      surface_point.y <= video_rect.y + video_rect.w) {
+    vec2 frame_texcoord =
+        (surface_point - video_rect.xy) / video_rect.zw;
     float y = 1.16438356 *
-            (texture2D(y_texture, video_texcoord).r - 16.0 / 255.0);
+              (texture2D(y_texture, frame_texcoord).r - 16.0 / 255.0);
-  vec2 uv = texture2D(uv_texture, video_texcoord).ra - vec2(0.5, 0.5);
+    vec2 uv =
-  vec3 rgb = vec3(y + 1.59602678 * uv.y,
+        texture2D(uv_texture, frame_texcoord).ra - vec2(0.5, 0.5);
+    rgb = clamp(vec3(y + 1.59602678 * uv.y,
                      y - 0.39176229 * uv.x - 0.81296764 * uv.y,
-                  y + 2.01723214 * uv.x);
+                     y + 2.01723214 * uv.x),
-  gl_FragColor = vec4(clamp(rgb, 0.0, 1.0), 1.0);
+                0.0, 1.0);
+  }
+  float coverage = 1.0;
+  if (corner_radius > 0.0) {
+    vec2 half_size = target_size * 0.5;
+    vec2 corner = abs(surface_point - half_size) -
+                  (half_size - vec2(corner_radius));
+    float distance_to_edge =
+        length(max(corner, vec2(0.0))) +
+        min(max(corner.x, corner.y), 0.0) - corner_radius;
+    coverage = clamp(0.5 - distance_to_edge, 0.0, 1.0);
+  }
+  gl_FragColor = vec4(rgb * coverage, coverage);
 }
 )glsl";
 
@@ -363,8 +445,19 @@ void main() {
       impl_->gl.get_uniform_location(impl_->program, "y_texture");
   impl_->uv_texture_location =
       impl_->gl.get_uniform_location(impl_->program, "uv_texture");
+  impl_->target_size_location =
+      impl_->gl.get_uniform_location(impl_->program, "target_size");
+  impl_->video_rect_location =
+      impl_->gl.get_uniform_location(impl_->program, "video_rect");
+  impl_->corner_radius_location =
+      impl_->gl.get_uniform_location(impl_->program, "corner_radius");
+  impl_->video_enabled_location =
+      impl_->gl.get_uniform_location(impl_->program, "video_enabled");
   if (impl_->position_location < 0 || impl_->texcoord_location < 0 ||
-      impl_->y_texture_location < 0 || impl_->uv_texture_location < 0) {
+      impl_->y_texture_location < 0 || impl_->uv_texture_location < 0 ||
+      impl_->target_size_location < 0 || impl_->video_rect_location < 0 ||
+      impl_->corner_radius_location < 0 ||
+      impl_->video_enabled_location < 0) {
     LOG_ERROR("OpenGL NV12 program is missing required shader bindings");
     impl_->gl.delete_program(impl_->program);
     impl_->ResetGlHandles();
@@ -429,7 +522,7 @@ void main() {
   return true;
 }
 
-void WindowsOpenGlVideoRenderer::Teardown() {
+void OpenGlVideoRenderer::Teardown() {
   impl_->ready.store(false, std::memory_order_release);
   if (impl_->y_texture != 0)
     glDeleteTextures(1, &impl_->y_texture);
@@ -444,11 +537,11 @@ void WindowsOpenGlVideoRenderer::Teardown() {
   impl_->ResetGlHandles();
 }
 
-bool WindowsOpenGlVideoRenderer::IsReady() const {
+bool OpenGlVideoRenderer::IsReady() const {
   return impl_->ready.load(std::memory_order_acquire);
 }
 
-bool WindowsOpenGlVideoRenderer::SetSelectedStream(std::string remote_id) {
+bool OpenGlVideoRenderer::SetSelectedStream(std::string remote_id) {
   std::lock_guard lock(impl_->frames->mutex);
   if (impl_->frames->selected_stream == remote_id) {
     return false;
@@ -463,7 +556,7 @@ bool WindowsOpenGlVideoRenderer::SetSelectedStream(std::string remote_id) {
   return true;
 }
 
-void WindowsOpenGlVideoRenderer::DiscardStream(std::string_view remote_id) {
+void OpenGlVideoRenderer::DiscardStream(std::string_view remote_id) {
   std::lock_guard lock(impl_->frames->mutex);
   for (auto &slot : impl_->frames->slots) {
     if (slot.remote_id == remote_id && slot.use != SlotUse::uploading) {
@@ -477,22 +570,22 @@ void WindowsOpenGlVideoRenderer::DiscardStream(std::string_view remote_id) {
   }
 }
 
-WindowsOpenGlVideoRenderer::SubmitResult
+OpenGlVideoRenderer::SubmitResult
-WindowsOpenGlVideoRenderer::SubmitNv12(std::string_view remote_id,
+OpenGlVideoRenderer::SubmitNv12(std::string_view remote_id,
                                        const uint8_t *data, size_t size,
                                        int width, int height) {
   return SubmitNv12Internal(remote_id, data, size, width, height, true);
 }
 
-WindowsOpenGlVideoRenderer::SubmitResult
+OpenGlVideoRenderer::SubmitResult
-WindowsOpenGlVideoRenderer::SubmitCachedNv12(std::string_view remote_id,
+OpenGlVideoRenderer::SubmitCachedNv12(std::string_view remote_id,
                                              const uint8_t *data, size_t size,
                                              int width, int height) {
   return SubmitNv12Internal(remote_id, data, size, width, height, false);
 }
 
-WindowsOpenGlVideoRenderer::SubmitResult
+OpenGlVideoRenderer::SubmitResult
-WindowsOpenGlVideoRenderer::SubmitNv12Internal(std::string_view remote_id,
+OpenGlVideoRenderer::SubmitNv12Internal(std::string_view remote_id,
                                                const uint8_t *data, size_t size,
                                                int width, int height,
                                                bool replace_pending) {
@@ -562,10 +655,11 @@ WindowsOpenGlVideoRenderer::SubmitNv12Internal(std::string_view remote_id,
   return SubmitResult::submitted;
 }
 
-WindowsOpenGlVideoRenderer::RenderOutcome
+OpenGlVideoRenderer::RenderOutcome
-WindowsOpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
+OpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
                                   int target_width, int target_height,
-                                         int top_inset_pixels) {
+                                  int top_inset_pixels,
+                                  int corner_radius_pixels) {
   if (!IsReady() || target_width <= 0 || target_height <= 0) {
     return {RenderResult::failed};
   }
@@ -643,7 +737,10 @@ WindowsOpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
   glDisable(GL_STENCIL_TEST);
   glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
   glViewport(0, 0, target_width, target_height);
-  glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+  // The Slint items above this underlay are transparent around the custom
+  // window corners. Keep those pixels transparent so the compositor can show
+  // the desktop instead of an opaque black framebuffer clear.
+  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
   glClear(GL_COLOR_BUFFER_BIT);
 
   bool upload_succeeded = true;
@@ -696,34 +793,37 @@ WindowsOpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
     }
   }
 
-  RenderOutcome outcome{RenderResult::empty};
+  const int content_y = std::clamp(top_inset_pixels, 0, target_height);
-  if (upload_succeeded && impl_->uploaded_stream == remote_id &&
+  const int content_height = target_height - content_y;
-      impl_->texture_width > 0 && impl_->texture_height > 0) {
+  const bool has_video =
+      upload_succeeded && impl_->uploaded_stream == remote_id &&
+      impl_->texture_width > 0 && impl_->texture_height > 0 &&
+      content_height > 0;
+  int video_x = 0;
+  int video_y = content_y;
+  int video_width = target_width;
+  int video_height = content_height;
+  if (has_video) {
     source_width = impl_->texture_width;
     source_height = impl_->texture_height;
     sequence = impl_->uploaded_sequence;
-    const int video_height = std::max(
-        0, target_height - std::clamp(top_inset_pixels, 0, target_height));
-    if (video_height > 0) {
     const double source_aspect =
         static_cast<double>(source_width) / source_height;
     const double target_aspect =
-          static_cast<double>(target_width) / video_height;
+        static_cast<double>(target_width) / content_height;
-      int viewport_width = target_width;
-      int viewport_height = video_height;
-      int viewport_x = 0;
-      int viewport_y = 0;
     if (source_aspect > target_aspect) {
-        viewport_height =
+      video_height =
           std::max(1, static_cast<int>(target_width / source_aspect + 0.5));
-        viewport_y = (video_height - viewport_height) / 2;
+      video_y = content_y + (content_height - video_height) / 2;
     } else {
-        viewport_width =
+      video_width =
-            std::max(1, static_cast<int>(video_height * source_aspect + 0.5));
+          std::max(1, static_cast<int>(content_height * source_aspect + 0.5));
-        viewport_x = (target_width - viewport_width) / 2;
+      video_x = (target_width - video_width) / 2;
+    }
   }
 
-      glViewport(viewport_x, viewport_y, viewport_width, viewport_height);
+  while (glGetError() != GL_NO_ERROR) {
+  }
   impl_->gl.use_program(impl_->program);
   impl_->gl.active_texture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_2D, impl_->y_texture);
@@ -731,6 +831,18 @@ WindowsOpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
   impl_->gl.active_texture(GL_TEXTURE1);
   glBindTexture(GL_TEXTURE_2D, impl_->uv_texture);
   impl_->gl.uniform_1i(impl_->uv_texture_location, 1);
+  impl_->gl.uniform_2f(impl_->target_size_location,
+                       static_cast<GLfloat>(target_width),
+                       static_cast<GLfloat>(target_height));
+  impl_->gl.uniform_4f(
+      impl_->video_rect_location, static_cast<GLfloat>(video_x),
+      static_cast<GLfloat>(video_y), static_cast<GLfloat>(video_width),
+      static_cast<GLfloat>(video_height));
+  impl_->gl.uniform_1f(
+      impl_->corner_radius_location,
+      static_cast<GLfloat>(std::clamp(
+          corner_radius_pixels, 0, std::min(target_width, target_height) / 2)));
+  impl_->gl.uniform_1f(impl_->video_enabled_location, has_video ? 1.0f : 0.0f);
   impl_->gl.bind_buffer(GL_ARRAY_BUFFER, impl_->vertex_buffer);
   impl_->gl.vertex_attrib_pointer(
       static_cast<GLuint>(impl_->position_location), 2, GL_FLOAT, GL_FALSE,
@@ -744,11 +856,13 @@ WindowsOpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
   impl_->gl.enable_vertex_attrib_array(
       static_cast<GLuint>(impl_->texcoord_location));
   glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
-      outcome = {glGetError() == GL_NO_ERROR ? RenderResult::rendered
+  const GLenum draw_error = glGetError();
-                                             : RenderResult::failed,
+  RenderOutcome outcome{
-                 source_width, source_height, sequence};
+      !upload_succeeded || draw_error != GL_NO_ERROR
-    }
+          ? RenderResult::failed
-  }
+          : has_video ? RenderResult::rendered : RenderResult::empty,
+      has_video ? source_width : 0, has_video ? source_height : 0,
+      has_video ? sequence : 0};
 
   RestoreVertexAttrib(impl_->gl, static_cast<GLuint>(impl_->position_location),
                       position_state);
@@ -786,7 +900,7 @@ WindowsOpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
   return outcome;
 }
 
-bool WindowsOpenGlVideoRenderer::CopyLatestNv12(
+bool OpenGlVideoRenderer::CopyLatestNv12(
     std::string_view remote_id, std::vector<unsigned char> *output, int *width,
     int *height) const {
   if (!output || !width || !height) {

src/gui/platform/opengl_video_renderer.h

@@ -1,5 +1,5 @@
-#ifndef CROSSDESK_GUI_PLATFORM_WINDOWS_OPENGL_VIDEO_RENDERER_H_
+#ifndef CROSSDESK_GUI_PLATFORM_OPENGL_VIDEO_RENDERER_H_
-#define CROSSDESK_GUI_PLATFORM_WINDOWS_OPENGL_VIDEO_RENDERER_H_
+#define CROSSDESK_GUI_PLATFORM_OPENGL_VIDEO_RENDERER_H_
 
 #include <cstddef>
 #include <cstdint>
@@ -10,11 +10,12 @@
 
 namespace crossdesk {
 
-// Windows NV12 underlay for Slint's FemtoVG OpenGL renderer. MiniRTC submits
+// NV12 underlay for Slint's FemtoVG OpenGL renderer on Windows and Linux.
-// tightly packed CPU NV12 frames from its decode callback thread. The Slint UI
+// MiniRTC submits tightly packed CPU NV12 frames from its decode callback
-// thread uploads the newest frame as Y and UV textures and performs color
+// thread. The Slint UI thread uploads the newest frame as Y and UV textures and
-// conversion and scaling in a fragment shader before Slint draws its overlay.
+// performs color conversion and scaling in a fragment shader before Slint
-class WindowsOpenGlVideoRenderer {
+// draws its overlay.
+class OpenGlVideoRenderer {
 public:
   enum class SubmitResult {
     submitted,
@@ -37,12 +38,11 @@ public:
     uint64_t sequence = 0;
   };
 
-  WindowsOpenGlVideoRenderer();
+  OpenGlVideoRenderer();
-  ~WindowsOpenGlVideoRenderer();
+  ~OpenGlVideoRenderer();
 
-  WindowsOpenGlVideoRenderer(const WindowsOpenGlVideoRenderer &) = delete;
+  OpenGlVideoRenderer(const OpenGlVideoRenderer &) = delete;
-  WindowsOpenGlVideoRenderer &
+  OpenGlVideoRenderer &operator=(const OpenGlVideoRenderer &) = delete;
-  operator=(const WindowsOpenGlVideoRenderer &) = delete;
 
   // These methods must run while Slint's OpenGL context is current, from the
   // RenderingSetup and RenderingTeardown notifier states respectively.
@@ -61,10 +61,12 @@ public:
   SubmitResult SubmitCachedNv12(std::string_view remote_id, const uint8_t *data,
                                 size_t size, int width, int height);
 
-  // Draws below Slint while its OpenGL context is current. target dimensions
+  // Draws below Slint while its OpenGL context is current. All dimensions are
-  // and top_inset_pixels are physical pixels in the window client area.
+  // physical pixels in the window client area. corner_radius_pixels clips the
+  // underlay to Slint's custom rounded window surface.
   RenderOutcome RenderLatest(std::string_view remote_id, int target_width,
-                             int target_height, int top_inset_pixels);
+                             int target_height, int top_inset_pixels,
+                             int corner_radius_pixels);
 
   // Used during disconnect cleanup so thumbnail generation does not require a
   // second per-frame CPU copy during normal playback.
@@ -83,4 +85,4 @@ private:
 
 } // namespace crossdesk
 
-#endif // CROSSDESK_GUI_PLATFORM_WINDOWS_OPENGL_VIDEO_RENDERER_H_
+#endif // CROSSDESK_GUI_PLATFORM_OPENGL_VIDEO_RENDERER_H_

src/gui/runtime/connection_runtime.cpp

@@ -11,8 +11,8 @@
 #include "display_stream_id.h"
 #include "localization.h"
 #include "platform.h"
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-#include "platform/windows_opengl_video_renderer.h"
+#include "platform/opengl_video_renderer.h"
 #endif
 #ifdef __APPLE__
 #include "platform/metal_video_renderer.h"
@@ -229,7 +229,7 @@ void GuiRuntime::CloseRemoteSession(std::shared_ptr<RemoteSession> props) {
     frame_snapshot = props->front_frame_;
     video_width = props->video_width_;
     video_height = props->video_height_;
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
     if ((!frame_snapshot || frame_snapshot->empty()) &&
         props->thumbnail_frame_ && !props->thumbnail_frame_->empty()) {
       frame_snapshot = props->thumbnail_frame_;
@@ -238,11 +238,11 @@ void GuiRuntime::CloseRemoteSession(std::shared_ptr<RemoteSession> props) {
     }
 #endif
   }
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
-#if defined(_WIN32)
+#if defined(__APPLE__)
-  auto* native_renderer = windows_opengl_video_renderer_.get();
-#else
   auto* native_renderer = mac_metal_video_renderer_.get();
+#else
+  auto* native_renderer = opengl_video_renderer_.get();
 #endif
   if ((!frame_snapshot || frame_snapshot->empty()) && native_renderer) {
     auto native_snapshot = std::make_shared<std::vector<unsigned char>>();
@@ -276,7 +276,7 @@ void GuiRuntime::CloseRemoteSession(std::shared_ptr<RemoteSession> props) {
     }
   }
 
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
   if (native_renderer) {
     native_renderer->DiscardStream(props->remote_id_);
     video_frame_dirty_.store(true, std::memory_order_release);
@@ -343,7 +343,7 @@ void GuiRuntime::ResetRemoteSessionResources(
     std::lock_guard<std::mutex> lock(props->video_frame_mutex_);
     props->front_frame_.reset();
     props->back_frame_.reset();
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
     props->thumbnail_frame_.reset();
     props->thumbnail_width_ = 0;
     props->thumbnail_height_ = 0;

src/gui/runtime/gui_runtime.cpp

@@ -12,8 +12,8 @@
 
 #include "display_stream_id.h"
 #include "localization.h"
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-#include "platform/windows_opengl_video_renderer.h"
+#include "platform/opengl_video_renderer.h"
 #endif
 #ifdef __APPLE__
 #include "platform/metal_video_renderer.h"

src/gui/runtime/gui_runtime.h

@@ -15,8 +15,8 @@
 
 namespace crossdesk {
 
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-class WindowsOpenGlVideoRenderer;
+class OpenGlVideoRenderer;
 #endif
 #ifdef __APPLE__
 class MacMetalVideoRenderer;
@@ -90,8 +90,8 @@ class GuiRuntime : protected gui_detail::GuiState {
   KeyboardController keyboard_;
   PeerEventHandler peer_events_;
   std::atomic<bool> video_frame_dirty_{false};
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-  std::unique_ptr<WindowsOpenGlVideoRenderer> windows_opengl_video_renderer_;
+  std::unique_ptr<OpenGlVideoRenderer> opengl_video_renderer_;
 #endif
 #ifdef __APPLE__
   std::unique_ptr<MacMetalVideoRenderer> mac_metal_video_renderer_;

src/gui/runtime/peer_event_handler.cpp

@@ -16,8 +16,8 @@
 #include "file_transfer.h"
 #include "localization.h"
 #include "platform.h"
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__linux__)
-#include "platform/windows_opengl_video_renderer.h"
+#include "platform/opengl_video_renderer.h"
 #endif
 #ifdef __APPLE__
 #include "platform/metal_video_renderer.h"
@@ -319,7 +319,7 @@ void PeerEventHandler::OnConnectionStatus(ConnectionStatus status,
         props->enable_mouse_control_ = false;
         runtime->ResetRemoteServiceStatus(*props);
 
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
         std::shared_ptr<std::vector<unsigned char>> native_snapshot;
         int native_snapshot_width = 0;
         int native_snapshot_height = 0;
@@ -330,11 +330,10 @@ void PeerEventHandler::OnConnectionStatus(ConnectionStatus status,
                                   props->thumbnail_frame_->empty();
         }
         if (needs_native_snapshot) {
-#if defined(_WIN32)
+#if defined(__APPLE__)
-          auto* native_renderer =
-              runtime->windows_opengl_video_renderer_.get();
-#else
           auto* native_renderer = runtime->mac_metal_video_renderer_.get();
+#else
+          auto* native_renderer = runtime->opengl_video_renderer_.get();
 #endif
           auto snapshot = std::make_shared<std::vector<unsigned char>>();
           if (native_renderer && native_renderer->CopyLatestNv12(
@@ -349,7 +348,7 @@ void PeerEventHandler::OnConnectionStatus(ConnectionStatus status,
           std::lock_guard<std::mutex> lock(props->video_frame_mutex_);
           props->front_frame_.reset();
           props->back_frame_.reset();
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
           if (native_snapshot &&
               (!props->thumbnail_frame_ || props->thumbnail_frame_->empty())) {
             props->thumbnail_frame_ = std::move(native_snapshot);
@@ -363,11 +362,11 @@ void PeerEventHandler::OnConnectionStatus(ConnectionStatus status,
           props->render_rect_dirty_ = true;
           props->stream_cleanup_pending_ = true;
         }
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
-#if defined(_WIN32)
+#if defined(__APPLE__)
-        auto* native_renderer = runtime->windows_opengl_video_renderer_.get();
-#else
         auto* native_renderer = runtime->mac_metal_video_renderer_.get();
+#else
+        auto* native_renderer = runtime->opengl_video_renderer_.get();
 #endif
         if (native_renderer) {
           native_renderer->DiscardStream(remote_id);

src/gui/runtime/peer_media_callbacks.cpp

@@ -7,18 +7,18 @@
 #include <vector>
 
 #include "runtime/gui_runtime.h"
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
 #include <chrono>
 
-#if defined(_WIN32)
+#if defined(__APPLE__)
-#include "platform/windows_opengl_video_renderer.h"
-#else
 #include "platform/metal_video_renderer.h"
+#else
+#include "platform/opengl_video_renderer.h"
 #endif
 #endif
 
 namespace crossdesk {
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
 namespace {
 
 constexpr auto kBackgroundSnapshotInterval = std::chrono::seconds(1);
@@ -45,14 +45,14 @@ void PeerEventHandler::OnReceiveVideoBuffer(
       runtime->remote_sessions_.find(remote_id)->second.get();
 
   if (props->connection_established_) {
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
     bool background_snapshot_only = false;
-#if defined(_WIN32)
+#if defined(__APPLE__)
-    auto* native_renderer = runtime->windows_opengl_video_renderer_.get();
-    using NativeVideoRenderer = WindowsOpenGlVideoRenderer;
-#else
     auto* native_renderer = runtime->mac_metal_video_renderer_.get();
     using NativeVideoRenderer = MacMetalVideoRenderer;
+#else
+    auto* native_renderer = runtime->opengl_video_renderer_.get();
+    using NativeVideoRenderer = OpenGlVideoRenderer;
 #endif
     if (native_renderer && native_renderer->IsReady()
 #if defined(__APPLE__)
@@ -101,7 +101,7 @@ void PeerEventHandler::OnReceiveVideoBuffer(
 #endif
     {
       std::lock_guard<std::mutex> lock(props->video_frame_mutex_);
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
       const auto now = std::chrono::steady_clock::now();
       if (background_snapshot_only && props->thumbnail_frame_ &&
           !props->thumbnail_frame_->empty() &&
@@ -137,7 +137,7 @@ void PeerEventHandler::OnReceiveVideoBuffer(
       props->video_size_ = video_frame->size;
 
       props->front_frame_.swap(props->back_frame_);
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
       props->thumbnail_frame_ = props->front_frame_;
       props->thumbnail_width_ = video_frame->width;
       props->thumbnail_height_ = video_frame->height;
@@ -149,7 +149,7 @@ void PeerEventHandler::OnReceiveVideoBuffer(
     }
 
     props->streaming_ = true;
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
     if (background_snapshot_only) {
       return;
     }

src/gui/runtime/remote_session.h

@@ -110,7 +110,7 @@ struct RemoteSession {
   std::mutex video_frame_mutex_;
   std::shared_ptr<std::vector<unsigned char>> front_frame_;
   std::shared_ptr<std::vector<unsigned char>> back_frame_;
-#if defined(__APPLE__) || defined(_WIN32)
+#if defined(__APPLE__) || defined(_WIN32) || defined(__linux__)
   // Retains the most recent background CPU frame across disconnect cleanup
   // so closing an unselected tab can still update its recent-item thumbnail.
   std::shared_ptr<std::vector<unsigned char>> thumbnail_frame_;

xmake/targets.lua

@@ -279,7 +279,7 @@ function setup_targets()
             add_cxxflags("/bigobj")
             add_links("opengl32")
             add_files("src/gui/platform/tray/win_tray.cpp",
-                "src/gui/platform/windows_opengl_video_renderer.cpp")
+                "src/gui/platform/opengl_video_renderer.cpp")
             add_includedirs("src/service/windows", {public = true})
         elseif is_os("macosx") then
             add_files("src/gui/runtime/*.mm", "src/gui/platform/tray/*.mm",
@@ -287,7 +287,8 @@ function setup_targets()
                 "src/gui/platform/metal_video_renderer.mm")
         elseif is_os("linux") then
             add_links("GL")
-            add_files("src/gui/platform/tray/linux_tray.cpp")
+            add_files("src/gui/platform/tray/linux_tray.cpp",
+                "src/gui/platform/opengl_video_renderer.cpp")
         end
 
     if is_os("windows") then