[client] renderers: only rebuild the font atlas if marked dirty

client/include/interface/renderer.h

@@ -33,6 +33,7 @@
    (x)->deinitialize    && \
    (x)->onRestart       && \
    (x)->onResize        && \
+   (x)->onFontUpdate    && \
    (x)->onMouseShape    && \
    (x)->onMouseEvent    && \
    (x)->renderStartup   && \
@@ -185,6 +186,10 @@ typedef struct LG_RendererOps
       const double scale, const LG_RendererRect destRect,
       LG_RendererRotate rotate);
 
+  /* called when the Dear ImGui font atlas texture must be uploaded
+   * Context: renderThread */
+  bool (*onFontUpdate)(LG_Renderer * renderer);
+
   /* called when the mouse shape has changed
    * Context: cursorThread */
   bool (*onMouseShape)(LG_Renderer * renderer, const LG_RendererCursor cursor,

client/renderers/EGL/egl.c

@@ -584,16 +584,18 @@ static void egl_onResize(LG_Renderer * renderer, const int width, const int heig
       !egl_hdrComposeResize(this->hdrCompose, this->width, this->height))
     DEBUG_FATAL("Failed to resize the linear HDR composition framebuffer");
 
-  // this is needed to refresh the font atlas texture
-  ImGui_ImplOpenGL3_Shutdown();
-  ImGui_ImplOpenGL3_Init("#version 300 es");
-  ImGui_ImplOpenGL3_NewFrame();
-  egl_stateInvalidate();
-
   egl_damageResize(this->damage, this->translateX, this->translateY, this->scaleX, this->scaleY);
   egl_desktopResize(this->desktop, this->width, this->height);
 }
 
+static bool egl_onFontUpdate(LG_Renderer * renderer)
+{
+  ImGui_ImplOpenGL3_DestroyFontsTexture();
+  const bool result = ImGui_ImplOpenGL3_CreateFontsTexture();
+  egl_stateInvalidate();
+  return result;
+}
+
 static bool egl_onMouseShape(LG_Renderer * renderer, const LG_RendererCursor cursor,
     const int width, const int height,
     const int pitch, const uint8_t * data)
@@ -1650,6 +1652,7 @@ struct LG_RendererOps LGR_EGL =
   .getInterop            = egl_getInterop,
   .onRestart             = egl_onRestart,
   .onResize              = egl_onResize,
+  .onFontUpdate          = egl_onFontUpdate,
   .onMouseShape          = egl_onMouseShape,
   .onMouseColorTransform = egl_onMouseColorTransform,
   .onMouseWhiteLevel     = egl_onMouseWhiteLevel,

client/renderers/OpenGL/opengl.c

@@ -314,11 +314,12 @@ void opengl_onResize(LG_Renderer * renderer, const int width, const int height,
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0, this->window.x, this->window.y, 0, -1, 1);
+}
 
-  // this is needed to refresh the font atlas texture
-  ImGui_ImplOpenGL2_Shutdown();
-  ImGui_ImplOpenGL2_Init();
-  ImGui_ImplOpenGL2_NewFrame();
+static bool opengl_onFontUpdate(LG_Renderer * renderer)
+{
+  ImGui_ImplOpenGL2_DestroyFontsTexture();
+  return ImGui_ImplOpenGL2_CreateFontsTexture();
 }
 
 bool opengl_onMouseShape(LG_Renderer * renderer, const LG_RendererCursor cursor,
@@ -744,6 +745,7 @@ const LG_RendererOps LGR_OpenGL =
   .deinitialize  = opengl_deinitialize,
   .onRestart     = opengl_onRestart,
   .onResize      = opengl_onResize,
+  .onFontUpdate  = opengl_onFontUpdate,
   .onMouseShape  = opengl_onMouseShape,
   .onMouseEvent  = opengl_onMouseEvent,
   .onFrameFormat = opengl_onFrameFormat,

client/src/app.c

@@ -1157,7 +1157,7 @@ void app_registerImGuiText(const char * text)
   if (!util_uiFontAddText(text))
     return;
 
-  atomic_fetch_add(&g_state.lgrResize, 1);
+  atomic_store(&g_state.fontDirty, true);
   app_invalidateOverlay(false);
 }
 

client/src/main.c

@@ -268,11 +268,23 @@ static int renderThread(void * unused)
         .y = g_state.windowScale,
       };
       g_state.io->FontGlobalScale = 1.0f / g_state.windowScale;
+    }
 
+    const bool fontDirty = atomic_exchange(&g_state.fontDirty, false);
+    if (unlikely(fontDirty || g_state.fontScale != g_state.windowScale))
+    {
       if (!util_buildUIFontAtlas(g_state.io->Fonts,
             g_params.uiSize * g_state.windowScale, &g_state.fontLarge))
         DEBUG_FATAL("Failed to build font atlas: %s (%s)", g_params.uiFont, g_state.fontName);
 
+      if (g_state.lgr && !RENDERER(onFontUpdate))
+        DEBUG_FATAL("Failed to upload the ImGui font atlas");
+
+      g_state.fontScale = g_state.windowScale;
+    }
+
+    if (unlikely(resize))
+    {
       if (g_state.lgr)
         RENDERER(onResize, g_state.windowW, g_state.windowH,
             g_state.windowScale, g_state.dstRect, g_params.winRotate);

client/src/main.h

@@ -106,6 +106,7 @@ struct AppState
   int                  windowW, windowH;
   int                  windowCX, windowCY;
   double               windowScale;
+  double               fontScale;
   LG_RendererRotate    rotate;
   bool                 focused;
   struct Border        border;
@@ -120,6 +121,7 @@ struct AppState
 
   LG_Renderer        * lgr;
   atomic_int           lgrResize;
+  atomic_bool          fontDirty;
   LG_Lock              lgrLock;
   bool                 useDMA;