Examples: Explicitly adding -DIMGUI_IMPL_OPENGL_LOADER_GL3W to Makefile to match linking settings

(otherwise if another loader such as Glew is accessible, the opengl3 backend might automatically use it). [#2919, #2798]

docs/CHANGELOG.txt

@@ -41,6 +41,9 @@ Other Changes:
 - Misc: Added ImGuiMouseCursor_NotAllowed enum so it can be used by more shared widgets. [@rokups]
 - Backends: GLFW, SDL, Win32, OSX, Allegro: Added support for ImGuiMouseCursor_NotAllowed. [@rokups]
 - Backends: GLFW: Added support for the missing mouse cursors newly added in GLFW 3.4+. [@rokups]
+- Examples: Explicitly adding -DIMGUI_IMPL_OPENGL_LOADER_GL3W to Makefile to match linking
+  settings (otherwise if another loader such as Glew is accessible, the opengl3 backend might
+  automatically use it). [#2919, #2798]
 - Examples: Metal: Wrapped main loop in @autoreleasepool block to ensure allocations get freed
   even if underlying system event loop gets paused due to app nap (#2910, #2917). [@bear24rw]
 

examples/example_glfw_opengl2/Makefile

@@ -52,7 +52,7 @@ ifeq ($(findstring MINGW,$(UNAME_S)),MINGW)
 	ECHO_MESSAGE = "MinGW"
 	LIBS += -lglfw3 -lgdi32 -lopengl32 -limm32
 
-	CXXFLAGS += -I../libs/gl3w `pkg-config --cflags glfw3`
+	CXXFLAGS += `pkg-config --cflags glfw3`
 	CFLAGS = $(CXXFLAGS)
 endif
 

examples/example_glfw_opengl3/Makefile

@@ -31,7 +31,7 @@ LIBS =
 
 ## Using OpenGL loader: gl3w [default]
 SOURCES += ../libs/gl3w/GL/gl3w.c
-CXXFLAGS += -I../libs/gl3w
+CXXFLAGS += -I../libs/gl3w -DIMGUI_IMPL_OPENGL_LOADER_GL3W
 
 ## Using OpenGL loader: glew
 ## (This assumes a system-wide installation)

examples/example_null/Makefile

@@ -65,10 +65,6 @@ endif
 %.o:../../%.cpp
 	$(CXX) $(CXXFLAGS) -c -o $@ $<
 
-%.o:../libs/gl3w/GL/%.c
-# %.o:../libs/glad/src/%.c
-	$(CC) $(CFLAGS) -c -o $@ $<
-
 all: $(EXE)
 	@echo Build complete for $(ECHO_MESSAGE)
 

examples/example_sdl_opengl3/Makefile

@@ -31,7 +31,7 @@ LIBS =
 
 ## Using OpenGL loader: gl3w [default]
 SOURCES += ../libs/gl3w/GL/gl3w.c
-CXXFLAGS += -I../libs/gl3w
+CXXFLAGS += -I../libs/gl3w -DIMGUI_IMPL_OPENGL_LOADER_GL3W
 
 ## Using OpenGL loader: glew
 ## (This assumes a system-wide installation)