imgui_impl_win32.cpp

// dear imgui: Platform Binding for Windows (standard windows API for 32 and 64 bits applications)
// This needs to be used along with a Renderer (e.g. DirectX11, OpenGL3, Vulkan..)
#include "imgui.h"
#include "imgui_impl_win32.h"
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>
#include <tchar.h>
// Win32 Data
static HWND                 g_hWnd = 0;
static INT64                g_Time = 0;
static INT64                g_TicksPerSecond = 0;
static ImGuiMouseCursor     g_LastMouseCursor = ImGuiMouseCursor_COUNT;

// Functions
bool    ImGui_ImplWin32_Init(void* hwnd)
{
	if (!::QueryPerformanceFrequency((LARGE_INTEGER *)&g_TicksPerSecond))
		return false;
	if (!::QueryPerformanceCounter((LARGE_INTEGER *)&g_Time))
		return false;

	// Setup back-end capabilities flags
	g_hWnd = (HWND)hwnd;
	ImGuiIO& io = ImGui::GetIO();
	io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;         // We can honor GetMouseCursor() values (optional)
	io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
	io.ImeWindowHandle = hwnd;

	// Keyboard mapping. ImGui will use those indices to peek into the io.KeysDown[] array that we will update during the application lifetime.
	io.KeyMap[ImGuiKey_Tab] = VK_TAB;
	io.KeyMap[ImGuiKey_LeftArrow] = VK_LEFT;
	io.KeyMap[ImGuiKey_RightArrow] = VK_RIGHT;
	io.KeyMap[ImGuiKey_UpArrow] = VK_UP;
	io.KeyMap[ImGuiKey_DownArrow] = VK_DOWN;
	io.KeyMap[ImGuiKey_PageUp] = VK_PRIOR;
	io.KeyMap[ImGuiKey_PageDown] = VK_NEXT;
	io.KeyMap[ImGuiKey_Home] = VK_HOME;
	io.KeyMap[ImGuiKey_End] = VK_END;
	io.KeyMap[ImGuiKey_Insert] = VK_INSERT;
	io.KeyMap[ImGuiKey_Delete] = VK_DELETE;
	io.KeyMap[ImGuiKey_Backspace] = VK_BACK;
	io.KeyMap[ImGuiKey_Space] = VK_SPACE;
	io.KeyMap[ImGuiKey_Enter] = VK_RETURN;
	io.KeyMap[ImGuiKey_Escape] = VK_ESCAPE;
	io.KeyMap[ImGuiKey_A] = 'A';
	io.KeyMap[ImGuiKey_C] = 'C';
	io.KeyMap[ImGuiKey_V] = 'V';
	io.KeyMap[ImGuiKey_X] = 'X';
	io.KeyMap[ImGuiKey_Y] = 'Y';
	io.KeyMap[ImGuiKey_Z] = 'Z';

	return true;
}

void    ImGui_ImplWin32_Shutdown()
{
	g_hWnd = (HWND)0;
}

static bool ImGui_ImplWin32_UpdateMouseCursor()
{
	ImGuiIO& io = ImGui::GetIO();
	if (io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange)
		return false;

	ImGuiMouseCursor imgui_cursor = ImGui::GetMouseCursor();
	if (imgui_cursor == ImGuiMouseCursor_None || io.MouseDrawCursor)
	{
		// Hide OS mouse cursor if imgui is drawing it or if it wants no cursor
		::SetCursor(NULL);
	}
	else
	{
		// Show OS mouse cursor
		LPTSTR win32_cursor = IDC_ARROW;
		switch (imgui_cursor)
		{
		case ImGuiMouseCursor_Arrow:        win32_cursor = IDC_ARROW; break;
		case ImGuiMouseCursor_TextInput:    win32_cursor = IDC_IBEAM; break;
		case ImGuiMouseCursor_ResizeAll:    win32_cursor = IDC_SIZEALL; break;
		case ImGuiMouseCursor_ResizeEW:     win32_cursor = IDC_SIZEWE; break;
		case ImGuiMouseCursor_ResizeNS:     win32_cursor = IDC_SIZENS; break;
		case ImGuiMouseCursor_ResizeNESW:   win32_cursor = IDC_SIZENESW; break;
		case ImGuiMouseCursor_ResizeNWSE:   win32_cursor = IDC_SIZENWSE; break;
		case ImGuiMouseCursor_Hand:         win32_cursor = IDC_HAND; break;
		}
		::SetCursor(::LoadCursor(NULL, win32_cursor));
	}
	return true;
}

static void ImGui_ImplWin32_UpdateMousePos()
{
	ImGuiIO& io = ImGui::GetIO();

	// Set OS mouse position if requested (rarely used, only when ImGuiConfigFlags_NavEnableSetMousePos is enabled by user)
	if (io.WantSetMousePos)
	{
		POINT pos = { (int)io.MousePos.x, (int)io.MousePos.y };
		::ClientToScreen(g_hWnd, &pos);
		::SetCursorPos(pos.x, pos.y);
	}

	// Set mouse position
	io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
	POINT pos;
	if (::GetForegroundWindow() == g_hWnd && ::GetCursorPos(&pos))
		if (::ScreenToClient(g_hWnd, &pos))
			io.MousePos = ImVec2((float)pos.x, (float)pos.y);
}

void    ImGui_ImplWin32_NewFrame()
{
	ImGuiIO& io = ImGui::GetIO();

	// Setup display size (every frame to accommodate for window resizing)
	RECT rect;
	::GetClientRect(g_hWnd, &rect);
	io.DisplaySize = ImVec2((float)(rect.right - rect.left), (float)(rect.bottom - rect.top));

	// Setup time step
	INT64 current_time;
	::QueryPerformanceCounter((LARGE_INTEGER *)&current_time);
	io.DeltaTime = (float)(current_time - g_Time) / g_TicksPerSecond;
	g_Time = current_time;

	// Read keyboard modifiers inputs
	io.KeyCtrl = (::GetKeyState(VK_CONTROL) & 0x8000) != 0;
	io.KeyShift = (::GetKeyState(VK_SHIFT) & 0x8000) != 0;
	io.KeyAlt = (::GetKeyState(VK_MENU) & 0x8000) != 0;
	io.KeySuper = false;
	// io.KeysDown[], io.MousePos, io.MouseDown[], io.MouseWheel: filled by the WndProc handler below.

	// Update OS mouse position
	ImGui_ImplWin32_UpdateMousePos();

	// Update OS mouse cursor with the cursor requested by imgui
	ImGuiMouseCursor mouse_cursor = io.MouseDrawCursor ? ImGuiMouseCursor_None : ImGui::GetMouseCursor();
	if (g_LastMouseCursor != mouse_cursor)
	{
		g_LastMouseCursor = mouse_cursor;
		ImGui_ImplWin32_UpdateMouseCursor();
	}
}

// Allow compilation with old Windows SDK. MinGW doesn't have default _WIN32_WINNT/WINVER versions.
#ifndef WM_MOUSEHWHEEL
#define WM_MOUSEHWHEEL 0x020E
#endif

// Process Win32 mouse/keyboard inputs. 
// You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
// - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application.
// - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
// Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
// PS: In this Win32 handler, we use the capture API (GetCapture/SetCapture/ReleaseCapture) to be able to read mouse coordinations when dragging mouse outside of our window bounds.
// PS: We treat DBLCLK messages as regular mouse down messages, so this code will work on windows classes that have the CS_DBLCLKS flag set. Our own example app code doesn't set this flag.
IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	if (ImGui::GetCurrentContext() == NULL)
		return 0;

	ImGuiIO& io = ImGui::GetIO();
	switch (msg)
	{
	case WM_MOUSEMOVE:
		ImGui_ImplWin32_UpdateMousePos();
		break;
	case WM_LBUTTONDOWN: case WM_LBUTTONDBLCLK:
	case WM_RBUTTONDOWN: case WM_RBUTTONDBLCLK:
	case WM_MBUTTONDOWN: case WM_MBUTTONDBLCLK:
	{
		int button = 0;
		if (msg == WM_LBUTTONDOWN || msg == WM_LBUTTONDBLCLK) button = 0;
		if (msg == WM_RBUTTONDOWN || msg == WM_RBUTTONDBLCLK) button = 1;
		if (msg == WM_MBUTTONDOWN || msg == WM_MBUTTONDBLCLK) button = 2;
		//     if (!ImGui::IsAnyMouseDown() && ::GetCapture() == NULL)
		//         ::SetCapture(hwnd);
		io.MouseDown[button] = true;
		return 0;
	}
	case WM_LBUTTONUP:
	case WM_RBUTTONUP:
	case WM_MBUTTONUP:
	{
		int button = 0;
		if (msg == WM_LBUTTONUP) button = 0;
		if (msg == WM_RBUTTONUP) button = 1;
		if (msg == WM_MBUTTONUP) button = 2;
		io.MouseDown[button] = false;
		//   if (!ImGui::IsAnyMouseDown() && ::GetCapture() == hwnd)
		//       ::ReleaseCapture();
		return 0;
	}
	case WM_MOUSEWHEEL:
		io.MouseWheel += (float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA;
		return 0;
	case WM_MOUSEHWHEEL:
		io.MouseWheelH += (float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA;
		return 0;
	case WM_KEYDOWN:
	case WM_SYSKEYDOWN:
		if (wParam < 256)
			io.KeysDown[wParam] = 1;
		return 0;
	case WM_KEYUP:
	case WM_SYSKEYUP:
	if (wParam < 256) io.KeysDown[wParam] = 0; return 0; case WM_CHAR: // You can also use ToAscii()+GetKeyboardState() to retrieve characters. if (wParam > 0 && wParam < 0x10000)
		io.AddInputCharacter((unsigned short)wParam);
		return 0;
	case WM_SETCURSOR:
		if (LOWORD(lParam) == HTCLIENT && ImGui_ImplWin32_UpdateMouseCursor())
			return 1;
		return 0;
	}
	return 0;
}