Added IMGUI_CHECKVERSION() macro to compare version string and data structure sizes in order to catch issues with mismatching compilation unit settings. (#1695, #1769)

CHANGELOG.txt

@@ -57,7 +57,9 @@ Other Changes:
 - InputText: On Mac OS X, filter out characters when the Cmd modifier is held. (#1747) [@sivu]
 - InputText: On Mac OS X, support Cmd+Shift+Z for Redo. Cmd+Y is also supported as major apps seems to default to support both. (#1765) [@lfnoise]
 - Style: Changed default style.DisplaySafeAreaPadding values from (4,4) to (3,3) so it is smaller than FramePadding and has no effect on main menu bar on a computer. (#1439)
+- Misc: Added IMGUI_CHECKVERSION() macro to compare version string and data structure sizes in order to catch issues with mismatching compilation unit settings. (#1695, #1769)
 - Demo: Fixed Overlay: Added a context menu item to enable freely moving the window. 
+- Examples: Calling IMGUI_CHECKVERSION() in the main.cpp of every example application.
 - Examples: Allegro 5: Added support for 32-bit indices setup via defining ImDrawIdx, to avoid an unnecessary conversion (Allegro 5 doesn't support 16-bit indices).
 - Examples: Allegro 5: Renamed bindings from imgui_impl_a5.cpp to imgui_impl_allegro5.cpp.
 - Various minor fixes, tweaks, refactoring, comments.

examples/allegro5_example/main.cpp

@@ -22,7 +22,8 @@ int main(int, char**)
     al_register_event_source(queue, al_get_keyboard_event_source());
     al_register_event_source(queue, al_get_mouse_event_source());
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/directx10_example/main.cpp

@@ -111,7 +111,8 @@ int main(int, char**)
     ShowWindow(hwnd, SW_SHOWDEFAULT);
     UpdateWindow(hwnd);
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/directx11_example/main.cpp

@@ -114,7 +114,8 @@ int main(int, char**)
     ShowWindow(hwnd, SW_SHOWDEFAULT);
     UpdateWindow(hwnd);
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/directx12_example/main.cpp

@@ -285,7 +285,8 @@ int main(int, char**)
     ShowWindow(hwnd, SW_SHOWDEFAULT);
     UpdateWindow(hwnd);
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/directx9_example/main.cpp

@@ -74,7 +74,8 @@ int main(int, char**)
         return 0;
     }
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/marmalade_example/main.cpp

@@ -16,7 +16,8 @@ int main(int, char**)
 {
     IwGxInit();
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/null_example/main.cpp

@@ -4,6 +4,7 @@
 
 int main(int, char**)
 {
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO();
 

examples/opengl2_example/main.cpp

@@ -26,7 +26,8 @@ int main(int, char**)
     glfwMakeContextCurrent(window);
     glfwSwapInterval(1); // Enable vsync
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/opengl3_example/main.cpp

@@ -31,7 +31,8 @@ int main(int, char**)
     glfwSwapInterval(1); // Enable vsync
     gl3wInit();
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/sdl_opengl2_example/main.cpp

@@ -33,7 +33,8 @@ int main(int, char**)
     SDL_GLContext gl_context = SDL_GL_CreateContext(window);
     SDL_GL_SetSwapInterval(1); // Enable vsync
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/sdl_opengl3_example/main.cpp

@@ -33,7 +33,8 @@ int main(int, char**)
     SDL_GL_SetSwapInterval(1); // Enable vsync
     gl3wInit();
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls

examples/vulkan_example/main.cpp

@@ -625,7 +625,8 @@ int main(int, char**)
     setup_vulkan(window);
     glfwSetFramebufferSizeCallback(window, glfw_resize_callback);
 
-    // Setup ImGui binding
+    // Setup Dear ImGui binding
+    IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     ImGui_ImplGlfwVulkan_Init_Data init_data = {};

imgui.cpp

@@ -2644,6 +2644,20 @@ void ImGui::SetCurrentContext(ImGuiContext* ctx)
 #endif
 }
 
+// Helper function to verify that the type sizes are matching between the calling file's compilation unit and imgui.cpp's compilation unit
+// If the user has inconsistent compilation settings, imgui configuration #define, packing pragma, etc. you may see different structures from what imgui.cpp sees which is highly problematic.
+bool ImGui::DebugCheckVersionAndDataLayout(const char* version, size_t sz_io, size_t sz_style, size_t sz_vec2, size_t sz_vec4, size_t sz_vert)
+{
+    bool error = false;
+    if (strcmp(version, IMGUI_VERSION)!=0) { error = true; IM_ASSERT(strcmp(version,IMGUI_VERSION)==0 && "Mismatch version string!");  }
+    if (sz_io    != sizeof(ImGuiIO))       { error = true; IM_ASSERT(sz_io    == sizeof(ImGuiIO)      && "Mismatched struct layout!"); }
+    if (sz_style != sizeof(ImGuiStyle))    { error = true; IM_ASSERT(sz_style == sizeof(ImGuiStyle)   && "Mismatched struct layout!"); }
+    if (sz_vec2  != sizeof(ImVec2))        { error = true; IM_ASSERT(sz_vec2  == sizeof(ImVec2)       && "Mismatched struct layout!"); }
+    if (sz_vec4  != sizeof(ImVec4))        { error = true; IM_ASSERT(sz_vec4  == sizeof(ImVec4)       && "Mismatched struct layout!"); }
+    if (sz_vert  != sizeof(ImDrawVert))    { error = true; IM_ASSERT(sz_vert  == sizeof(ImDrawVert)   && "Mismatched struct layout!"); }
+    return !error;
+}
+
 void ImGui::SetAllocatorFunctions(void* (*alloc_func)(size_t sz, void* user_data), void(*free_func)(void* ptr, void* user_data), void* user_data)
 {
     GImAllocatorAllocFunc = alloc_func;

imgui.h

@@ -21,20 +21,20 @@
 #include <stddef.h>                 // ptrdiff_t, NULL
 #include <string.h>                 // memset, memmove, memcpy, strlen, strchr, strcpy, strcmp
 
+// Version
 #define IMGUI_VERSION               "1.61 WIP"
+#define IMGUI_CHECKVERSION()        ImGui::DebugCheckVersionAndDataLayout(IMGUI_VERSION, sizeof(ImGuiIO), sizeof(ImGuiStyle), sizeof(ImVec2), sizeof(ImVec4), sizeof(ImDrawVert))
 
-// Define attributes of all API symbols declarations, e.g. for DLL under Windows.
+// Define attributes of all API symbols declarations (e.g. for DLL under Windows)
 #ifndef IMGUI_API
 #define IMGUI_API
 #endif
 
-// Define assertion handler.
+// Helpers
 #ifndef IM_ASSERT
 #include <assert.h>
 #define IM_ASSERT(_EXPR)            assert(_EXPR)
 #endif
-
-// Helpers
 #if defined(__clang__) || defined(__GNUC__)
 #define IM_FMTARGS(FMT)             __attribute__((format(printf, FMT, FMT+1))) // Apply printf-style warnings to user functions.
 #define IM_FMTLIST(FMT)             __attribute__((format(printf, FMT, 0)))
@@ -60,7 +60,7 @@ struct ImDrawVert;                  // A single vertex (20 bytes by default, ove
 struct ImFont;                      // Runtime data for a single font within a parent ImFontAtlas
 struct ImFontAtlas;                 // Runtime data for multiple fonts, bake multiple fonts into a single texture, TTF/OTF font loader
 struct ImFontConfig;                // Configuration data when adding a font or merging fonts
-struct ImColor;                     // Helper functions to create a color that can be converted to either u32 or float4
+struct ImColor;                     // Helper functions to create a color that can be converted to either u32 or float4 (*obsolete* please avoid using)
 struct ImGuiIO;                     // Main configuration and I/O between your application and ImGui
 struct ImGuiOnceUponAFrame;         // Simple helper for running a block of code not more than once a frame, used by IMGUI_ONCE_UPON_A_FRAME macro
 struct ImGuiStorage;                // Simple custom key value storage
@@ -143,6 +143,7 @@ namespace ImGui
     IMGUI_API void          DestroyContext(ImGuiContext* ctx = NULL);   // NULL = destroy current context
     IMGUI_API ImGuiContext* GetCurrentContext();
     IMGUI_API void          SetCurrentContext(ImGuiContext* ctx);
+    IMGUI_API bool          DebugCheckVersionAndDataLayout(const char* version_str, size_t sz_io, size_t sz_style, size_t sz_vec2, size_t sz_vec4, size_t sz_drawvert);
 
     // Main
     IMGUI_API ImGuiIO&      GetIO();