Backends: Amend, docs + extra comments. (#3330, #3245)

docs/CHANGELOG.txt

@@ -45,6 +45,7 @@ Other Changes:
   - Clear ImFontAtlasFlags_NoBakedLines in ImFontAtlas::Flags to disable baking data in texture.
 - ImDrawList: Fixed minor bug introduced in 1.75 where AddCircle() with 12 segments would generate
   an extra vertex. (This bug was mistakenly marked as fixed in earlier 1.77 release). [@ShironekoBen]
+- Backends: OpenGL3: Added support for glad2 loader. (#3330) [@moritz-h]
 
 
 -----------------------------------------------------------------------

examples/README.txt

@@ -204,7 +204,7 @@ example_glfw_opengl2/
     GLFW + OpenGL2 example (legacy, fixed pipeline).
     = main.cpp + imgui_impl_glfw.cpp + imgui_impl_opengl2.cpp
     **DO NOT USE OPENGL2 CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
-    **Prefer using OPENGL3 code (with gl3w/glew/glad/glbinding, you can replace the OpenGL function loader)**
+    **Prefer using OPENGL3 code (with gl3w/glew/glad/glad2/glbinding, you can replace the OpenGL function loader)**
     This code is mostly provided as a reference to learn about Dear ImGui integration, because it is shorter.
     If your code is using GL3+ context or any semi modern OpenGL calls, using this renderer is likely to
     make things more complicated, will require your code to reset many OpenGL attributes to their initial
@@ -253,7 +253,7 @@ example_sdl_opengl2/
     SDL2 (Win32, Mac, Linux etc.) + OpenGL example (legacy, fixed pipeline).
     = main.cpp + imgui_impl_sdl.cpp + imgui_impl_opengl2.cpp
     **DO NOT USE OPENGL2 CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
-    **Prefer using OPENGL3 code (with gl3w/glew/glad/glbinding, you can replace the OpenGL function loader)**
+    **Prefer using OPENGL3 code (with gl3w/glew/glad/glad2/glbinding, you can replace the OpenGL function loader)**
     This code is mostly provided as a reference to learn about Dear ImGui integration, because it is shorter.
     If your code is using GL3+ context or any semi modern OpenGL calls, using this renderer is likely to
     make things more complicated, will require your code to reset many OpenGL attributes to their initial

examples/example_glfw_opengl3/main.cpp

@@ -87,7 +87,7 @@ int main(int, char**)
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
     bool err = gladLoadGL() == 0;
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-    bool err = gladLoadGL(glfwGetProcAddress) == 0; // glad docs recommend using the windowing library loader instead of the (optionally) bundled one.
+    bool err = gladLoadGL(glfwGetProcAddress) == 0; // glad2 recommend using the windowing library loader instead of the (optionally) bundled one.
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
     bool err = false;
     glbinding::Binding::initialize();

examples/example_sdl_opengl3/main.cpp

@@ -82,7 +82,7 @@ int main(int, char**)
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
     bool err = gladLoadGL() == 0;
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-    bool err = gladLoadGL((GLADloadfunc) SDL_GL_GetProcAddress) == 0; // glad docs recommend using the windowing library loader instead of the (optionally) bundled one.
+    bool err = gladLoadGL((GLADloadfunc)SDL_GL_GetProcAddress) == 0; // glad2 recommend using the windowing library loader instead of the (optionally) bundled one.
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
     bool err = false;
     glbinding::Binding::initialize();

examples/imgui_impl_opengl3.cpp

@@ -13,7 +13,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
-//  2020-07-01: OpenGL: Added support for glad2 OpenGL loader.
+//  2020-07-10: OpenGL: Added support for glad2 OpenGL loader.
 //  2020-05-08: OpenGL: Made default GLSL version 150 (instead of 130) on OSX.
 //  2020-04-21: OpenGL: Fixed handling of glClipControl(GL_UPPER_LEFT) by inverting projection matrix.
 //  2020-04-12: OpenGL: Fixed context version check mistakenly testing for 4.0+ instead of 3.2+ to enable ImGuiBackendFlags_RendererHasVtxOffset.

imgui_draw.cpp

@@ -717,8 +717,11 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
             // [PATH 1] Texture-based lines (thick or non-thick)
             // [PATH 2] Non texture-based lines (non-thick)
 
-            // The width of the geometry we need to draw - this is essentially <thickness> pixels for the line itself, plus one pixel for AA
+            // The width of the geometry we need to draw - this is essentially <thickness> pixels for the line itself, plus "one pixel" for AA.
-            // We don't use AA_SIZE here because the +1 is tied to the generated texture and so alternate values won't work without changes to that code
+            // - In the texture-based path, we don't use AA_SIZE here because the +1 is tied to the generated texture
+            //   (see ImFontAtlasBuildRenderLinesTexData() function), and so alternate values won't work without changes to that code.
+            // - In the non texture-based paths, we would allow AA_SIZE to potentially be != 1.0f with a patch (e.g. fringe_scale patch to
+            //   allow scaling geometry while preserving one-screen-pixel AA fringe).
             const float half_draw_size = use_texture ? ((thickness * 0.5f) + 1) : AA_SIZE;
 
             // If line is not closed, the first and last points need to be generated differently as there are no normals to blend