Examples: OpenGL3: Tweaks, added changelog. (#1941)

CHANGELOG.txt

@@ -66,7 +66,8 @@ Other Changes:
  - Examples: OSX: Added early raw OSX platform backend. (#1873) [@pagghiu, @itamago, @ocornut]
  - Examples: Added mac OSX & iOS + Metal example in example_apple_metal/. (#1929, #1873) [@warrenm]
  - Examples: Added mac OSX + OpenGL2 example in example_apple_opengl2/. (#1873)
- - Examples: OpenGL3: Added shaders more versions of GLSL. (#1938, #1900, #1513, #1466, etc.) 
+ - Examples: OpenGL3: Added shaders more versions of GLSL. (#1938, #1941, #1900, #1513, #1466, etc.) 
+ - Examples: OpenGL3: Tweaked the imgui_impl_opengl3.cpp to work as-is with Emscripten + WebGL 2.0. (#1941). [@o-micron] 
  - Examples: OpenGL3: Made the example app default to GL 3.0 + GLSL 130 (instead of GL 3.2 + GLSL 150) unless on Mac.
  - Examples: OpenGL3: Added error output when shaders fail to compile/link.
  - Examples: DirectX10, DirectX11: Fixed unreleased resources in Init and Shutdown functions. (#1944)

examples/imgui_impl_opengl3.cpp

@@ -11,6 +11,7 @@
 
 // CHANGELOG 
 // (minor and older changes stripped away, please see git history for details)
+//  2018-07-30: OpenGL: Support for GLSL 300 ES and 410 core. Fixes for Emscripten compilation.
 //  2018-07-10: OpenGL: Support for more GLSL versions (based on the GLSL version string). Added error output when shaders fail to compile/link.
 //  2018-06-08: Misc: Extracted imgui_impl_opengl3.cpp/.h away from the old combined GLFW/SDL+OpenGL3 examples.
 //  2018-06-08: OpenGL: Use draw_data->DisplayPos and draw_data->DisplaySize to setup projection matrix and clipping rectangle.
@@ -58,13 +59,13 @@
 #endif
 
 #ifdef __EMSCRIPTEN__
-    #include <GLES3/gl3.h>
+#include <GLES3/gl3.h>  // Use GL ES 3
 #else
-    #include <GL/gl3w.h>    // This example is using gl3w to access OpenGL functions. You may use another OpenGL loader/header such as: glew, glext, glad, glLoadGen, etc.
+#include <GL/gl3w.h>    // This example is using gl3w to access OpenGL functions. You may use another OpenGL loader/header such as: glew, glext, glad, glLoadGen, etc.
-#endif
 //#include <glew.h>
 //#include <glext.h>
 //#include <glad/glad.h>
+#endif
 
 // OpenGL Data
 static char         g_GlslVersionString[32] = "";
@@ -118,9 +119,9 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
     GLint last_sampler; glGetIntegerv(GL_SAMPLER_BINDING, &last_sampler);
     GLint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
     GLint last_vertex_array; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
-    #ifdef GL_POLYGON_MODE
+#ifdef GL_POLYGON_MODE
     GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
-    #endif
+#endif
     GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
     GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
     GLenum last_blend_src_rgb; glGetIntegerv(GL_BLEND_SRC_RGB, (GLint*)&last_blend_src_rgb);
@@ -141,9 +142,9 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
     glDisable(GL_CULL_FACE);
     glDisable(GL_DEPTH_TEST);
     glEnable(GL_SCISSOR_TEST);
-    #ifdef glPolygonMode
+#ifdef GL_POLYGON_MODE
     glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
-    #endif
+#endif
 
     // Setup viewport, orthographic projection matrix
     // Our visible imgui space lies from draw_data->DisplayPps (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayMin is typically (0,0) for single viewport apps.
@@ -229,9 +230,9 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
     if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
     if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
     if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
-    #ifdef glPolygonMode
+#ifdef GL_POLYGON_MODE
     glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
-    #endif
+#endif
     glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
     glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
 }
@@ -425,21 +426,21 @@ bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
     // Select shaders matching our GLSL versions
     const GLchar* vertex_shader = NULL;
     const GLchar* fragment_shader = NULL;
-    if(glsl_version == 410)
+    if (glsl_version < 130)
+    {
+        vertex_shader = vertex_shader_glsl_120;
+        fragment_shader = fragment_shader_glsl_120;
+    }
+    else if (glsl_version == 410)
     {
         vertex_shader = vertex_shader_glsl_410_core;
         fragment_shader = fragment_shader_glsl_410_core;
     }
-    else if(glsl_version == 300)
+    else if (glsl_version == 300)
     {
         vertex_shader = vertex_shader_glsl_300_es;
         fragment_shader = fragment_shader_glsl_300_es;
     }
-    else if (glsl_version < 130)
-    {
-        vertex_shader = vertex_shader_glsl_120;
-        fragment_shader = fragment_shader_glsl_120;
-    }
     else
     {
         vertex_shader = vertex_shader_glsl_130;