Backends: Include imgui.h in implementation headers. (#3105)

Currently, the implementation headers don't include the imgui.h header.
Which means that the compilation will fail if the implementation header
was included before the imgui.h header in the compilation unit. For
instance, a compilation unit with the following will work:

  #include "imgui.h"
  #include "imgui_impl_glfw.h"
  #include "imgui_impl_opengl3.h"

But a compilation unit with the following will fail because IMGUI_IMPL_API
and possibly other symbols will not be defined:

  #include "imgui_impl_glfw.h"
  #include "imgui_impl_opengl3.h"
  #include "imgui.h"

This patch includes imgui.h in the implementation headers to make
inclusions order-invariant, which is a recommended practice.

examples/imgui_impl_allegro5.h

@@ -15,6 +15,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 struct ALLEGRO_DISPLAY;
 union ALLEGRO_EVENT;
 

examples/imgui_impl_dx10.h

@@ -11,6 +11,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 struct ID3D10Device;
 
 IMGUI_IMPL_API bool     ImGui_ImplDX10_Init(ID3D10Device* device);

examples/imgui_impl_dx11.h

@@ -11,6 +11,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 struct ID3D11Device;
 struct ID3D11DeviceContext;
 

examples/imgui_impl_dx12.h

@@ -13,6 +13,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 enum DXGI_FORMAT;
 struct ID3D12Device;
 struct ID3D12DescriptorHeap;

examples/imgui_impl_dx9.h

@@ -11,6 +11,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 struct IDirect3DDevice9;
 
 IMGUI_IMPL_API bool     ImGui_ImplDX9_Init(IDirect3DDevice9* device);

examples/imgui_impl_glfw.h

@@ -18,6 +18,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 struct GLFWwindow;
 
 IMGUI_IMPL_API bool     ImGui_ImplGlfw_InitForOpenGL(GLFWwindow* window, bool install_callbacks);

examples/imgui_impl_glut.h

@@ -17,6 +17,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 IMGUI_IMPL_API bool     ImGui_ImplGLUT_Init();
 IMGUI_IMPL_API void     ImGui_ImplGLUT_InstallFuncs();
 IMGUI_IMPL_API void     ImGui_ImplGLUT_Shutdown();

examples/imgui_impl_marmalade.h

@@ -10,6 +10,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 IMGUI_IMPL_API bool     ImGui_Marmalade_Init(bool install_callbacks);
 IMGUI_IMPL_API void     ImGui_Marmalade_Shutdown();
 IMGUI_IMPL_API void     ImGui_Marmalade_NewFrame();

examples/imgui_impl_metal.h

@@ -9,6 +9,8 @@
 // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
 // https://github.com/ocornut/imgui
 
+#include "imgui.h"
+
 @class MTLRenderPassDescriptor;
 @protocol MTLDevice, MTLCommandBuffer, MTLRenderCommandEncoder;
 

examples/imgui_impl_opengl2.h

@@ -18,6 +18,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 IMGUI_IMPL_API bool     ImGui_ImplOpenGL2_Init();
 IMGUI_IMPL_API void     ImGui_ImplOpenGL2_Shutdown();
 IMGUI_IMPL_API void     ImGui_ImplOpenGL2_NewFrame();

examples/imgui_impl_opengl3.h

@@ -23,6 +23,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 // Backend API
 IMGUI_IMPL_API bool     ImGui_ImplOpenGL3_Init(const char* glsl_version = NULL);
 IMGUI_IMPL_API void     ImGui_ImplOpenGL3_Shutdown();

examples/imgui_impl_osx.h

@@ -8,6 +8,8 @@
 // Issues:
 //  [ ] Platform: Keys are all generally very broken. Best using [event keycode] and not [event characters]..
 
+#include "imgui.h"
+
 @class NSEvent;
 @class NSView;
 

examples/imgui_impl_sdl.h

@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 struct SDL_Window;
 typedef union SDL_Event SDL_Event;
 

examples/imgui_impl_vulkan.h

@@ -22,6 +22,7 @@
 
 #pragma once
 
+#include "imgui.h"
 #include <vulkan/vulkan.h>
 
 // Initialization data, for ImGui_ImplVulkan_Init()

examples/imgui_impl_win32.h

@@ -9,6 +9,8 @@
 
 #pragma once
 
+#include "imgui.h"
+
 IMGUI_IMPL_API bool     ImGui_ImplWin32_Init(void* hwnd);
 IMGUI_IMPL_API void     ImGui_ImplWin32_Shutdown();
 IMGUI_IMPL_API void     ImGui_ImplWin32_NewFrame();