Backends: OpenGL3: Expose selected render state in ImGui_ImplOpenGL3_RenderState, allowing to dynamically select between use of glBindSampler() and glTexParameter(). (#9378)

2026-06-21 22:06:31 +00:00 · 2026-06-17 15:00:20 +02:00
parent 7aaf10f15b
commit 73a6610e81
3 changed files with 73 additions and 16 deletions
--- a/backends/imgui_impl_opengl3.cpp
+++ b/backends/imgui_impl_opengl3.cpp
@@ -23,7 +23,8 @@

 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
-//  2026-06-23: OpenGL: GLSL version detection assume GLSL 410 when GL context is 4.1. Fixes an issue running on macOS with Wine. (#9427, #6577)
+//  2026-06-17: OpenGL: Expose selected render state in ImGui_ImplOpenGL3_RenderState, Allowing to dynamically select between use of glBindSampler() and glTexParameter(). You can access in 'void* platform_io.Renderer_RenderState' during rendering.
+//  2026-06-03: OpenGL: GLSL version detection assume GLSL 410 when GL context is 4.1. Fixes an issue running on macOS with Wine. (#9427, #6577)
 //  2026-04-23: OpenGL: Added support for standard draw callbacks (in platform_io): DrawCallback_ResetRenderState, DrawCallback_SetSamplerLinear, DrawCallback_SetSamplerNearest. (#9378)
 //                      (Breaking): this change prioritize using glBindSampler() when available, which would override glTexParameter() settings you may have set on custom textures.
 //  2026-03-12: OpenGL: Fixed invalid assert in ImGui_ImplOpenGL3_UpdateTexture() if ImTextureID_Invalid is defined to be != 0, which became the default since 2026-03-12. (#9295)
@@ -255,8 +256,6 @@ struct ImGui_ImplOpenGL3_Data
    bool            HasBindSampler;
    bool            HasClipOrigin;
    bool            UseBufferSubData;
-    bool            UseTexParameterToSetSampler;
-    GLuint          NextSampler;            // Used if !HasBindSampler && UseTexParameterToSetSampler.
 #ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
    GLuint          TexSamplers[2];         // Used if HasBindSimpler. (0=linear, 1=nearest)
 #endif
@@ -332,7 +331,7 @@ void    ImGui_ImplOpenGL3_NewFrame()
            IM_ASSERT(0 && "ImGui_ImplOpenGL3_CreateDeviceObjects() failed!");
 }

-static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, int fb_width, int fb_height, GLuint vertex_array_object)
+static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, ImGui_ImplOpenGL3_RenderState* render_state, int fb_width, int fb_height, GLuint vertex_array_object)
 {
    ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();

@@ -386,8 +385,11 @@ static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, int fb_wid
    glUniformMatrix4fv(bd->AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);

 #ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
-    if (bd->HasBindSampler)
-        glBindSampler(0, bd->TexSamplers[0]); // We use combined texture/sampler state. Applications using GL 3.3 and GL ES 3.0 may set that otherwise.
+    if (render_state->UseBindSampler)
+    {
+        render_state->CurrentSampler = bd->TexSamplers[0];
+        glBindSampler(0, render_state->CurrentSampler); // We use combined texture/sampler state. Applications using GL 3.3 and GL ES 3.0 may set that otherwise.
+    }
 #endif

    (void)vertex_array_object;
@@ -408,13 +410,42 @@ static void ImGui_ImplOpenGL3_SetupRenderState(ImDrawData* draw_data, int fb_wid

 // Draw callbacks
 static void ImGui_ImplOpenGL3_DrawCallback_ResetRenderState(const ImDrawList*, const ImDrawCmd*)    {} // Intentionally empty. Used as an identifier for rendering loop to call its code. Simpler to implement this way.
+static void ImGui_ImplOpenGL3_DrawCallback_SetSamplerLinear(const ImDrawList*, const ImDrawCmd*)
+{
+    ImGui_ImplOpenGL3_RenderState* render_state = ImGui_ImplOpenGL3_GetRenderState();
 #ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
-static void ImGui_ImplOpenGL3_DrawCallback_SetSamplerLinear(const ImDrawList*, const ImDrawCmd*)    { ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData(); if (bd->HasBindSampler) { glBindSampler(0, bd->TexSamplers[0]); } else { bd->UseTexParameterToSetSampler = true; bd->NextSampler = GL_LINEAR; } }
-static void ImGui_ImplOpenGL3_DrawCallback_SetSamplerNearest(const ImDrawList*, const ImDrawCmd*)   { ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData(); if (bd->HasBindSampler) { glBindSampler(0, bd->TexSamplers[1]); } else { bd->UseTexParameterToSetSampler = true; bd->NextSampler = GL_NEAREST; } }
-#else
-static void ImGui_ImplOpenGL3_DrawCallback_SetSamplerLinear(const ImDrawList*, const ImDrawCmd*)    { ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData(); bd->UseTexParameterToSetSampler = true; bd->NextSampler = GL_LINEAR; }
-static void ImGui_ImplOpenGL3_DrawCallback_SetSamplerNearest(const ImDrawList*, const ImDrawCmd*)   { ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData(); bd->UseTexParameterToSetSampler = true; bd->NextSampler = GL_NEAREST; }
+    ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
+    if (bd->HasBindSampler)
+    {
+        render_state->CurrentSampler = bd->TexSamplers[0];
+        render_state->UseTexParameterFilter = false;
+        glBindSampler(0, render_state->CurrentSampler);
+    }
+    else
 #endif
+    {
+        render_state->UseTexParameterFilter = true;
+        render_state->CurrentTexParameterFilter = GL_LINEAR;
+    }
+}
+static void ImGui_ImplOpenGL3_DrawCallback_SetSamplerNearest(const ImDrawList*, const ImDrawCmd*)
+{
+    ImGui_ImplOpenGL3_RenderState* render_state = ImGui_ImplOpenGL3_GetRenderState();
+#ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_BIND_SAMPLER
+    ImGui_ImplOpenGL3_Data* bd = ImGui_ImplOpenGL3_GetBackendData();
+    if (bd->HasBindSampler)
+    {
+        render_state->CurrentSampler = bd->TexSamplers[1];
+        render_state->UseTexParameterFilter = false;
+        glBindSampler(0, render_state->CurrentSampler);
+    }
+    else
+#endif
+    {
+        render_state->UseTexParameterFilter = true;
+        render_state->CurrentTexParameterFilter = GL_NEAREST;
+    }
+}

 // OpenGL3 Render function.
 // Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly.
@@ -484,7 +515,17 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
 #ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
    GL_CALL(glGenVertexArrays(1, &vertex_array_object));
 #endif
-    ImGui_ImplOpenGL3_SetupRenderState(draw_data, fb_width, fb_height, vertex_array_object);
+
+    // Setup render state structure (for callbacks and custom texture bindings)
+    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
+    ImGui_ImplOpenGL3_RenderState render_state;
+    render_state.UseBindSampler = bd->HasBindSampler;
+    render_state.UseTexParameterFilter = false;
+    render_state.CurrentSampler = 0;
+    render_state.CurrentTexParameterFilter = 0;
+    platform_io.Renderer_RenderState = &render_state;
+
+    ImGui_ImplOpenGL3_SetupRenderState(draw_data, &render_state, fb_width, fb_height, vertex_array_object);

    // Will project scissor/clipping rectangles into framebuffer space
    ImVec2 clip_off = draw_data->DisplayPos;         // (0,0) unless using multi-viewports
@@ -531,7 +572,7 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
            {
                // User callback, registered via ImDrawList::AddCallback()
                if (pcmd->UserCallback == ImGui_ImplOpenGL3_DrawCallback_ResetRenderState)
-                    ImGui_ImplOpenGL3_SetupRenderState(draw_data, fb_width, fb_height, vertex_array_object);
+                    ImGui_ImplOpenGL3_SetupRenderState(draw_data, &render_state, fb_width, fb_height, vertex_array_object);
                else
                    pcmd->UserCallback(draw_list, pcmd);
            }
@@ -551,10 +592,10 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)

                // Emulate sampler change (even though it is technically part of texture data)
                // As a sort of hack/workaround, we only start writing using glTexParameter() if sampler is ever changed explicitly.
-                if (!bd->HasBindSampler && bd->UseTexParameterToSetSampler)
+                if (render_state.UseTexParameterFilter)
                {
-                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, bd->NextSampler);
-                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, bd->NextSampler);
+                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, render_state.CurrentTexParameterFilter);
+                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, render_state.CurrentTexParameterFilter);
                }

 #ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_VTX_OFFSET
@@ -566,6 +607,7 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
            }
        }
    }
+    platform_io.Renderer_RenderState = nullptr;

    // Destroy the temporary VAO
 #ifdef IMGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
--- a/backends/imgui_impl_opengl3.h
+++ b/backends/imgui_impl_opengl3.h
@@ -65,4 +65,17 @@ IMGUI_IMPL_API void     ImGui_ImplOpenGL3_UpdateTexture(ImTextureData* tex);

 #endif

+// [BETA] Selected render state data shared with callbacks.
+// This is temporarily stored in GetPlatformIO().Renderer_RenderState during the ImGui_ImplOpenGL3_RenderDrawData() call.
+// (Please open an issue if you feel you need access to more data)
+struct ImGui_ImplOpenGL3_RenderState
+{
+    bool            UseBindSampler;
+    bool            UseTexParameterFilter;
+    unsigned int    CurrentSampler;                 // (GLuint) Used if UseBindSampler == true, otherwise always 0
+    unsigned int    CurrentTexParameterFilter;      // (GLuint) Used if UseTexParameterToSetSampler == true
+};
+
+static inline ImGui_ImplOpenGL3_RenderState* ImGui_ImplOpenGL3_GetRenderState() { return (ImGui_ImplOpenGL3_RenderState*)ImGui::GetPlatformIO().Renderer_RenderState; }
+
 #endif // #ifndef IMGUI_DISABLE
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -86,6 +86,8 @@ Other Changes:
  - OpenGL3:
    - GLSL version detection assume GLSL 410 when GL context is 4.1.
      Fixes an issue running on macOS with Wine. [#9427, #6577) [@perminovVS]
+    - Expose selected render state in ImGui_ImplOpenGL3_RenderState, allowing to
+      dynamically select between use of glBindSampler() and glTexParameter(). (#9378)
  - Win32:
    - Uses `SetProcessDpiAwarenessContext()` instead of `SetThreadDpiAwarenessContext()`
      when available, fixing OpenGL DPI scaling issues as e.g. NVIDIA drivers tends