Backends: OpenGL3: Don't try to read GL_CLIP_ORIGIN unless we're OpenGL 4.5. (#3998, #2366, #2186)

backends/imgui_impl_opengl3.cpp

@@ -13,6 +13,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-04-06: OpenGL: Don't try to read GL_CLIP_ORIGIN unless we're OpenGL 4.5 or greater.
 //  2021-02-18: OpenGL: Change blending equation to preserve alpha in output buffer.
 //  2021-01-03: OpenGL: Backup, setup and restore GL_STENCIL_TEST state.
 //  2020-10-23: OpenGL: Backup, setup and restore GL_PRIMITIVE_RESTART state.
@@ -262,11 +263,14 @@ static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, int fb_wid
 #endif
 
     // Support for GL 4.5 rarely used glClipControl(GL_UPPER_LEFT)
-#if defined(GL_CLIP_ORIGIN) && !defined(__APPLE__)
+#if defined(GL_CLIP_ORIGIN)
     bool clip_origin_lower_left = true;
-    GLenum current_clip_origin = 0; glGetIntegerv(GL_CLIP_ORIGIN, (GLint*)&current_clip_origin);
+    if (g_GlVersion >= 450)
-    if (current_clip_origin == GL_UPPER_LEFT)
+    {
-        clip_origin_lower_left = false;
+        GLenum current_clip_origin = 0; glGetIntegerv(GL_CLIP_ORIGIN, (GLint*)&current_clip_origin);
+        if (current_clip_origin == GL_UPPER_LEFT)
+            clip_origin_lower_left = false;
+    }
 #endif
 
     // Setup viewport, orthographic projection matrix
@@ -276,7 +280,7 @@ static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, int fb_wid
     float R = draw_data->DisplayPos.x + draw_data->DisplaySize.x;
     float T = draw_data->DisplayPos.y;
     float B = draw_data->DisplayPos.y + draw_data->DisplaySize.y;
-#if defined(GL_CLIP_ORIGIN) && !defined(__APPLE__)
+#if defined(GL_CLIP_ORIGIN)
     if (!clip_origin_lower_left) { float tmp = T; T = B; B = tmp; } // Swap top and bottom if origin is upper left
 #endif
     const float ortho_projection[4][4] =

docs/CHANGELOG.txt

@@ -59,6 +59,7 @@ Other Changes:
   workaround/fix state restoring issues. Unknown exactly why so, but bit of a cargo-cult fix. (#3857)
 - Backends: Vulkan: Fix mapped memory Vulkan validation error when buffer sizes are not multiple of
   VkPhysicalDeviceLimits::nonCoherentAtomSize. (#3957) [@AgentX1994]
+- Backends: OpenGL3: Don't try to read GL_CLIP_ORIGIN unless we're OpenGL 4.5. (#3998, #2366, #2186) [@s7jones]
 - Examples: Add OpenGL ES 2.0 support to modern GL examples. (#2837, #3951) [@lethal-guitar, @hinxx]
 - Examples: Vulkan: Rebuild swapchain on VK_SUBOPTIMAL_KHR. (#3881)
 - Examples: SDL2: Link with shell32.lib required by SDL2main.lib since SDL 2.0.12. [#3988]