Examples: OpenGL3: Trying to make the call to glBindSampler optional to make the example code easier to use/share with different context version. (#1806)

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -121,7 +121,7 @@ void ImGui_ImplGlfwGL3_RenderDrawData(ImDrawData* draw_data)
     glUseProgram(g_ShaderHandle);
     glUniform1i(g_AttribLocationTex, 0);
     glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);
-    glBindSampler(0, 0); // Rely on combined texture/sampler state.
+    if (glBindSampler) glBindSampler(0, 0); // We use combined texture/sampler state. Applications using GL 3.3 may set that otherwise.
 
     // Recreate the VAO every time 
     // (This is to easily allow multiple GL contexts. VAO are not shared among GL contexts, and we don't track creation/deletion of windows so we don't have an obvious key to use to cache them.)
@@ -169,7 +169,7 @@ void ImGui_ImplGlfwGL3_RenderDrawData(ImDrawData* draw_data)
     // Restore modified GL state
     glUseProgram(last_program);
     glBindTexture(GL_TEXTURE_2D, last_texture);
-    glBindSampler(0, last_sampler);
+    if (glBindSampler) glBindSampler(0, last_sampler);
     glActiveTexture(last_active_texture);
     glBindVertexArray(last_vertex_array);
     glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);

examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp

@@ -119,7 +119,7 @@ void ImGui_ImplSdlGL3_RenderDrawData(ImDrawData* draw_data)
     glUseProgram(g_ShaderHandle);
     glUniform1i(g_AttribLocationTex, 0);
     glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);
-    glBindSampler(0, 0); // Rely on combined texture/sampler state.
+    if (glBindSampler) glBindSampler(0, 0); // We use combined texture/sampler state. Applications using GL 3.3 may set that otherwise.
 
     // Recreate the VAO every time 
     // (This is to easily allow multiple GL contexts. VAO are not shared among GL contexts, and we don't track creation/deletion of windows so we don't have an obvious key to use to cache them.)
@@ -167,7 +167,7 @@ void ImGui_ImplSdlGL3_RenderDrawData(ImDrawData* draw_data)
     // Restore modified GL state
     glUseProgram(last_program);
     glBindTexture(GL_TEXTURE_2D, last_texture);
-    glBindSampler(0, last_sampler);
+    if (glBindSampler) glBindSampler(0, last_sampler);
     glActiveTexture(last_active_texture);
     glBindVertexArray(last_vertex_array);
     glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);