Backends: OpenGL3: amend reset GL_POLYGON_MODE separately for front and back when possible. (#6333)

backends/imgui_impl_opengl3.cpp

@@ -14,6 +14,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2023-04-18: OpenGL: Restore front and back polygon mode separately when supported by context. (#6333)
 //  2023-03-23: OpenGL: Properly restoring "no shader program bound" if it was the case prior to running the rendering function. (#6267, #6220, #6224)
 //  2023-03-15: OpenGL: Fixed GL loader crash when GL_VERSION returns NULL. (#6154, #4445, #3530)
 //  2023-03-06: OpenGL: Fixed restoration of a potentially deleted OpenGL program, by calling glIsProgram(). (#6220, #6224)
@@ -204,6 +205,8 @@ struct ImGui_ImplOpenGL3_Data
 {
     GLuint          GlVersion;               // Extracted at runtime using GL_MAJOR_VERSION, GL_MINOR_VERSION queries (e.g. 320 for GL 3.2)
     char            GlslVersionString[32];   // Specified by user or detected based on compile time GL settings.
+    bool            GlProfileIsCompat;
+    GLint           GlProfileMask;
     GLuint          FontTexture;
     GLuint          ShaderHandle;
     GLint           AttribLocationTex;       // Uniforms location
@@ -284,6 +287,10 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
         sscanf(gl_version, "%d.%d", &major, &minor);
     }
     bd->GlVersion = (GLuint)(major * 100 + minor * 10);
+#if defined(GL_CONTEXT_PROFILE_MASK)
+    glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &bd->GlProfileMask);
+    bd->GlProfileIsCompat = (bd->GlProfileMask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT) != 0;
+#endif
 
     bd->UseBufferSubData = false;
     /*
@@ -613,22 +620,16 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
 #endif
 
 #ifdef IMGUI_IMPL_HAS_POLYGON_MODE
-// Desktop OpenGL 3.0 and OpenGL 3.1 had separate polygon draw modes for front-facing and back-facing faces of polygons
-#if defined(GL_FRONT) && defined(GL_BACK) // possibly Desktop OpenGL 3.0, 3.1 or 3.2+ compatibility profile
-#ifdef GL_CONTEXT_PROFILE_MASK // Desktop OpenGL 3.2+
-    GLint profile_mask;
-    glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &profile_mask);
-    if (profile_mask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT)
-#else
-    if (bd->GlVersion <= 310)
-#endif
+    // Desktop OpenGL 3.0 and OpenGL 3.1 had separate polygon draw modes for front-facing and back-facing faces of polygons
+    if (bd->GlVersion <= 310 || bd->GlProfileIsCompat)
     {
         glPolygonMode(GL_FRONT, (GLenum)last_polygon_mode[0]);
         glPolygonMode(GL_BACK, (GLenum)last_polygon_mode[1]);
     }
     else
-#endif // GL_FRONT & GL_BACK
-    glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
+    {
+        glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
+    }
 #endif // IMGUI_IMPL_HAS_POLYGON_MODE
 
     glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);

backends/imgui_impl_opengl3_loader.h

@@ -118,7 +118,7 @@ extern "C" {
 ** included as <GL/glcorearb.h>.
 **
 ** glcorearb.h includes only APIs in the latest OpenGL core profile
-** implementation together with APIs in newer ARB extensions which
+** implementation together with APIs in newer ARB extensions which 
 ** can be supported by the core profile. It does not, and never will
 ** include functionality removed from the core profile, such as
 ** fixed-function vertex and fragment processing.
@@ -154,6 +154,8 @@ typedef khronos_uint8_t GLubyte;
 #define GL_ONE                            1
 #define GL_SRC_ALPHA                      0x0302
 #define GL_ONE_MINUS_SRC_ALPHA            0x0303
+#define GL_FRONT                          0x0404
+#define GL_BACK                           0x0405
 #define GL_FRONT_AND_BACK                 0x0408
 #define GL_POLYGON_MODE                   0x0B40
 #define GL_CULL_FACE                      0x0B44
@@ -373,6 +375,8 @@ GLAPI void APIENTRY glGenVertexArrays (GLsizei n, GLuint *arrays);
 typedef struct __GLsync *GLsync;
 typedef khronos_uint64_t GLuint64;
 typedef khronos_int64_t GLint64;
+#define GL_CONTEXT_COMPATIBILITY_PROFILE_BIT 0x00000002
+#define GL_CONTEXT_PROFILE_MASK           0x9126
 typedef void (APIENTRYP PFNGLDRAWELEMENTSBASEVERTEXPROC) (GLenum mode, GLsizei count, GLenum type, const void *indices, GLint basevertex);
 typedef void (APIENTRYP PFNGLGETINTEGER64I_VPROC) (GLenum target, GLuint index, GLint64 *data);
 #ifdef GL_GLEXT_PROTOTYPES

docs/CHANGELOG.txt

@@ -48,6 +48,8 @@ Other changes:
   (#6341) [@lukaasm]
 - Backends: Clear bits sets io.BackendFlags on backend Shutdown(). (#6334, #6335] [@GereonV]
   Potentially this would facilitate switching runtime backend mid-session.
+- Backends: OpenGL3: Restore front and back polygon mode separately when supported
+  by context (Desktop 3.0, 3.1, or 3.2+ with compat bit). (#6333) [@GereonV]