Backends: OpenGL3: Tweaked initialization code allow application calling ImGui_ImplOpenGL3_CreateFontsTexture() before ImGui_ImplOpenGL3_NewFrame() if for some reason they wanted.

docs/CHANGELOG.txt

@@ -51,6 +51,8 @@ Other Changes:
 - Added a mechanism to compact/free the larger allocations of unused windows (buffers are compacted when
   a window is unused for 60 seconds, as per io.ConfigWindowsMemoryCompactTimer = 60.0f). Note that memory
   usage has never been reported as a problem, so this is merely a touch of overzealous luxury. (#2636)
+- Backends: OpenGL3: Tweaked initialization code allow application calling ImGui_ImplOpenGL3_CreateFontsTexture()
+  before ImGui_ImplOpenGL3_NewFrame() if for some reason they wanted.
 - Backends: DX11: Fixed GSGetShader() call not passing an initialized instance count,
   would generally make the debug layer complain (Added in 1.72).
 - Backends: Vulkan: Added support for specifying multisample count.

examples/imgui_impl_opengl3.cpp

@@ -13,6 +13,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2019-09-16: OpenGL: Tweak initialization code to allow application calling ImGui_ImplOpenGL3_CreateFontsTexture() before the first NewFrame() call.
 //  2019-05-29: OpenGL: Desktop GL only: Added support for large mesh (64K+ vertices), enable ImGuiBackendFlags_RendererHasVtxOffset flag.
 //  2019-04-30: OpenGL: Added support for special ImDrawCallback_ResetRenderState callback to reset render state.
 //  2019-03-29: OpenGL: Not calling glBindBuffer more than necessary in the render loop.
@@ -164,7 +165,7 @@ void    ImGui_ImplOpenGL3_Shutdown()
 
 void    ImGui_ImplOpenGL3_NewFrame()
 {
-    if (!g_FontTexture)
+    if (!g_ShaderHandle)
         ImGui_ImplOpenGL3_CreateDeviceObjects();
 }
 
@@ -613,20 +614,13 @@ bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
 
 void    ImGui_ImplOpenGL3_DestroyDeviceObjects()
 {
-    if (g_VboHandle) glDeleteBuffers(1, &g_VboHandle);
+    if (g_VboHandle)        { glDeleteBuffers(1, &g_VboHandle); g_VboHandle = 0; }
-    if (g_ElementsHandle) glDeleteBuffers(1, &g_ElementsHandle);
+    if (g_ElementsHandle)   { glDeleteBuffers(1, &g_ElementsHandle); g_ElementsHandle = 0; }
-    g_VboHandle = g_ElementsHandle = 0;
+    if (g_ShaderHandle && g_VertHandle) { glDetachShader(g_ShaderHandle, g_VertHandle); }
-
+    if (g_ShaderHandle && g_FragHandle) { glDetachShader(g_ShaderHandle, g_FragHandle); }
-    if (g_ShaderHandle && g_VertHandle) glDetachShader(g_ShaderHandle, g_VertHandle);
+    if (g_VertHandle)       { glDeleteShader(g_VertHandle); g_VertHandle = 0; }
-    if (g_VertHandle) glDeleteShader(g_VertHandle);
+    if (g_FragHandle)       { glDeleteShader(g_FragHandle); g_FragHandle = 0; }
-    g_VertHandle = 0;
+    if (g_ShaderHandle)     { glDeleteProgram(g_ShaderHandle); g_ShaderHandle = 0; }
-
-    if (g_ShaderHandle && g_FragHandle) glDetachShader(g_ShaderHandle, g_FragHandle);
-    if (g_FragHandle) glDeleteShader(g_FragHandle);
-    g_FragHandle = 0;
-
-    if (g_ShaderHandle) glDeleteProgram(g_ShaderHandle);
-    g_ShaderHandle = 0;
 
     ImGui_ImplOpenGL3_DestroyFontsTexture();
 }