Examples: OpenGL3: Added shaders more versions of GLSL + made the example app default to GL 3.0 + GLSL 130 (instead of GL 3.2 + GLSL 150) unless on Mac. (#1938, #1900, #1513, #1466, etc.)

CHANGELOG.txt

@@ -60,6 +60,8 @@ 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: 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: Win32, Glfw, SDL: Added support for the ImGuiMouseCursor_Hand cursor.
 

examples/example_glfw_opengl2/main.cpp

@@ -24,6 +24,8 @@ int main(int, char**)
     if (!glfwInit())
         return 1;
     GLFWwindow* window = glfwCreateWindow(1280, 720, "ImGui GLFW+OpenGL2 example", NULL, NULL);
+    if (window == NULL)
+        return 1;
     glfwMakeContextCurrent(window);
     glfwSwapInterval(1); // Enable vsync
 

examples/example_glfw_opengl3/main.cpp

@@ -26,13 +26,28 @@ int main(int, char**)
     glfwSetErrorCallback(glfw_error_callback);
     if (!glfwInit())
         return 1;
+
+    // Decide GL+GLSL versions
+#if __APPLE__
+    // GL 3.2 + GLSL 150
+    const char* glsl_version = "#version 150";
     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
-    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
-#if __APPLE__
-    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
+    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);  // 3.2+ only
+    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);            // Required on Mac
+#else
+    // GL 3.0 + GLSL 130
+    const char* glsl_version = "#version 130";
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
+    //glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);  // 3.2+ only
+    //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);            // 3.0+ only
 #endif
+
+    // Create window with graphics context
     GLFWwindow* window = glfwCreateWindow(1280, 720, "ImGui GLFW+OpenGL3 example", NULL, NULL);
+    if (window == NULL)
+        return 1;
     glfwMakeContextCurrent(window);
     glfwSwapInterval(1); // Enable vsync
     gl3wInit();
@@ -45,7 +60,7 @@ int main(int, char**)
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;   // Enable Gamepad Controls
 
     ImGui_ImplGlfw_InitForOpenGL(window, true);
-    ImGui_ImplOpenGL3_Init();
+    ImGui_ImplOpenGL3_Init(glsl_version);
 
     // Setup style
     ImGui::StyleColorsDark();

examples/example_sdl_opengl3/main.cpp

@@ -23,14 +23,27 @@ int main(int, char**)
         return -1;
     }
 
-    // Setup window
-    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG);
+    // Decide GL+GLSL versions
+#if __APPLE__
+    // GL 3.2 Core + GLSL 150
+    const char* glsl_version = "#version 150";
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG); // Always required on Mac
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
+#else
+    // GL 3.0 + GLSL 130
+    const char* glsl_version = "#version 130";
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
+#endif
+
+    // Create window with graphics context
     SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
     SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
     SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
-    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
-    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
     SDL_DisplayMode current;
     SDL_GetCurrentDisplayMode(0, &current);
     SDL_Window* window = SDL_CreateWindow("ImGui SDL2+OpenGL3 example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720, SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
@@ -45,7 +58,7 @@ int main(int, char**)
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
 
     ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
-    ImGui_ImplOpenGL3_Init();
+    ImGui_ImplOpenGL3_Init(glsl_version);
 
     // Setup style
     ImGui::StyleColorsDark();

examples/imgui_impl_opengl3.cpp

@@ -11,7 +11,7 @@
 
 // CHANGELOG 
 // (minor and older changes stripped away, please see git history for details)
-//  2018-07-10: OpenGL: Added error output when shaders fail to compile/link.
+//  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.
 //  2018-05-25: OpenGL: Removed unnecessary backup/restore of GL_ELEMENT_ARRAY_BUFFER_BINDING since this is part of the VAO state.
@@ -26,6 +26,24 @@
 //  2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
 //  2016-07-29: OpenGL: Explicitly setting GL_UNPACK_ROW_LENGTH to reduce issues because SDL changes it. (#752)
 
+//----------------------------------------
+// OpenGL    GLSL      GLSL
+// version   version   string
+//----------------------------------------
+//  2.0       110       "#version 110"
+//  2.1       120
+//  3.0       130
+//  3.1       140
+//  3.2       150       "#version 150"
+//  3.3       330
+//  4.0       400
+//  4.1       410
+//  4.2       420
+//  4.3       430
+//  ES 2.0    100       "#version 100"
+//  ES 3.0    300       "#version 300 es"
+//----------------------------------------
+
 #if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_WARNINGS)
 #define _CRT_SECURE_NO_WARNINGS
 #endif
@@ -40,7 +58,7 @@
 //#include <glad/glad.h>
 
 // OpenGL Data
-static char         g_GlslVersion[32] = "";
+static char         g_GlslVersionString[32] = "";
 static GLuint       g_FontTexture = 0;
 static GLuint       g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
 static int          g_AttribLocationTex = 0, g_AttribLocationProjMtx = 0;
@@ -52,10 +70,10 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
 {
     // Store GLSL version string so we can refer to it later in case we recreate shaders. Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
     if (glsl_version == NULL)
-        glsl_version = "#version 150";
-    IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(g_GlslVersion));
-    strcpy(g_GlslVersion, glsl_version);
-    strcat(g_GlslVersion, "\n");
+        glsl_version = "#version 130";
+    IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(g_GlslVersionString));
+    strcpy(g_GlslVersionString, glsl_version);
+    strcat(g_GlslVersionString, "\n");
     return true;
 }
 
@@ -285,8 +303,25 @@ bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
     glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
     glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
 
-    // Create shaders
-    const GLchar* vertex_shader =
+    // Parse GLSL version string
+    int glsl_version = 130;
+    sscanf(g_GlslVersionString, "#version %d", &glsl_version);
+
+    const GLchar* vertex_shader_glsl_120 =
+        "uniform mat4 ProjMtx;\n"
+        "attribute vec2 Position;\n"
+        "attribute vec2 UV;\n"
+        "attribute vec4 Color;\n"
+        "varying vec2 Frag_UV;\n"
+        "varying vec4 Frag_Color;\n"
+        "void main()\n"
+        "{\n"
+        "    Frag_UV = UV;\n"
+        "    Frag_Color = Color;\n"
+        "    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
+        "}\n";
+
+    const GLchar* vertex_shader_glsl_130 =
         "uniform mat4 ProjMtx;\n"
         "in vec2 Position;\n"
         "in vec2 UV;\n"
@@ -300,23 +335,50 @@ bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
         "    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
         "}\n";
 
-    const GLchar* fragment_shader =
+    const GLchar* fragment_shader_glsl_120 =
+        "#ifdef GL_ES\n"
+        "    precision mediump float;\n"
+        "#endif\n"
+        "uniform sampler2D Texture;\n"
+        "varying vec2 Frag_UV;\n"
+        "varying vec4 Frag_Color;\n"
+        "void main()\n"
+        "{\n"
+        "    gl_FragColor = Frag_Color * texture2D(Texture, Frag_UV.st);\n"
+        "}\n";
+
+    const GLchar* fragment_shader_glsl_130 =
         "uniform sampler2D Texture;\n"
         "in vec2 Frag_UV;\n"
         "in vec4 Frag_Color;\n"
         "out vec4 Out_Color;\n"
         "void main()\n"
         "{\n"
-        "	Out_Color = Frag_Color * texture( Texture, Frag_UV.st);\n"
+        "    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
         "}\n";
 
-    const GLchar* vertex_shader_with_version[2] = { g_GlslVersion, vertex_shader };
+    // Select shaders matching our GLSL versions
+    const GLchar* vertex_shader = NULL;
+    const GLchar* fragment_shader = NULL;
+    if (glsl_version < 130)
+    {
+        vertex_shader = vertex_shader_glsl_120;
+        fragment_shader = fragment_shader_glsl_120;
+    }
+    else
+    {
+        vertex_shader = vertex_shader_glsl_130;
+        fragment_shader = fragment_shader_glsl_130;
+    }
+
+    // Create shaders
+    const GLchar* vertex_shader_with_version[2] = { g_GlslVersionString, vertex_shader };
     g_VertHandle = glCreateShader(GL_VERTEX_SHADER);
     glShaderSource(g_VertHandle, 2, vertex_shader_with_version, NULL);
     glCompileShader(g_VertHandle);
     CheckShader(g_VertHandle, "vertex shader");
 
-    const GLchar* fragment_shader_with_version[2] = { g_GlslVersion, fragment_shader };
+    const GLchar* fragment_shader_with_version[2] = { g_GlslVersionString, fragment_shader };
     g_FragHandle = glCreateShader(GL_FRAGMENT_SHADER);
     glShaderSource(g_FragHandle, 2, fragment_shader_with_version, NULL);
     glCompileShader(g_FragHandle);

examples/imgui_impl_opengl3.h

@@ -10,8 +10,8 @@
 // https://github.com/ocornut/imgui
 
 // About GLSL version:
-// The 'glsl_version' initialization parameter defaults to "#version 150" if NULL.
-// Only override if your GL version doesn't handle this GLSL version. Keep NULL if unsure!
+// The 'glsl_version' initialization parameter defaults to "#version 130" if NULL.
+// Only override if your GL version doesn't handle this GLSL version (see table at the top of imgui_impl_opengl3.cpp). Keep NULL if unsure!
 
 IMGUI_IMPL_API bool     ImGui_ImplOpenGL3_Init(const char* glsl_version = NULL);
 IMGUI_IMPL_API void     ImGui_ImplOpenGL3_Shutdown();