Added OpenGL3 example for SDL2

examples/sdl_opengl3_example/README.md

@@ -0,0 +1,8 @@
+
+# How to Build
+
+Link
+=== 
+OpenGL
+SDL2
+GLEW

examples/sdl_opengl3_example/imgui_impl_sdlogl3.cpp

@@ -0,0 +1,379 @@
+// ImGui SDL2 binding with OpenGL3
+// https://github.com/ocornut/imgui
+
+#include <SDL.h>
+#include <SDL_syswm.h>
+#include <GL/glew.h>
+#include "imgui.h"
+#include "imgui_impl_sdlogl3.h"
+
+// Data
+static SDL_Window*  g_Window = NULL;
+static double       g_Time = 0.0f;
+static bool         g_MousePressed[3] = { false, false, false };
+static float        g_MouseWheel = 0.0f;
+static GLuint       g_FontTexture = 0;
+static int          g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
+static int          g_AttribLocationTex = 0, g_AttribLocationProjMtx = 0;
+static int          g_AttribLocationPosition = 0, g_AttribLocationUV = 0, g_AttribLocationColor = 0;
+static unsigned int g_VboHandle = 0, g_VaoHandle = 0, g_ElementsHandle = 0;
+
+// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
+// If text or lines are blurry when integrating ImGui in your engine:
+// - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
+void ImGui_ImplSdlOgl3_RenderDrawLists(ImDrawData* draw_data)
+{
+	// Backup GL state
+	GLint last_program; glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
+	GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
+	GLint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
+	GLint last_element_array_buffer; glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING, &last_element_array_buffer);
+	GLint last_vertex_array; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
+	GLint last_blend_src; glGetIntegerv(GL_BLEND_SRC, &last_blend_src);
+	GLint last_blend_dst; glGetIntegerv(GL_BLEND_DST, &last_blend_dst);
+	GLint last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, &last_blend_equation_rgb);
+	GLint last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, &last_blend_equation_alpha);
+	GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
+	GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
+	GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
+	GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);
+
+	// Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
+	glEnable(GL_BLEND);
+	glBlendEquation(GL_FUNC_ADD);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+	glDisable(GL_CULL_FACE);
+	glDisable(GL_DEPTH_TEST);
+	glEnable(GL_SCISSOR_TEST);
+	glActiveTexture(GL_TEXTURE0);
+
+	// Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
+	ImGuiIO& io = ImGui::GetIO();
+	float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
+	draw_data->ScaleClipRects(io.DisplayFramebufferScale);
+
+	// Setup orthographic projection matrix
+	const float ortho_projection[4][4] =
+	{
+		{ 2.0f / io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },
+		{ 0.0f,                  2.0f / -io.DisplaySize.y, 0.0f, 0.0f },
+		{ 0.0f,                  0.0f,                  -1.0f, 0.0f },
+		{ -1.0f,                  1.0f,                   0.0f, 1.0f },
+	};
+	glUseProgram(g_ShaderHandle);
+	glUniform1i(g_AttribLocationTex, 0);
+	glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);
+	glBindVertexArray(g_VaoHandle);
+
+	for (int n = 0; n < draw_data->CmdListsCount; n++)
+	{
+		const ImDrawList* cmd_list = draw_data->CmdLists[n];
+		const ImDrawIdx* idx_buffer_offset = 0;
+
+		glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
+		glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)cmd_list->VtxBuffer.size() * sizeof(ImDrawVert), (GLvoid*)&cmd_list->VtxBuffer.front(), GL_STREAM_DRAW);
+
+		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_ElementsHandle);
+		glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)cmd_list->IdxBuffer.size() * sizeof(ImDrawIdx), (GLvoid*)&cmd_list->IdxBuffer.front(), GL_STREAM_DRAW);
+
+		for (const ImDrawCmd* pcmd = cmd_list->CmdBuffer.begin(); pcmd != cmd_list->CmdBuffer.end(); pcmd++)
+		{
+			if (pcmd->UserCallback)
+			{
+				pcmd->UserCallback(cmd_list, pcmd);
+			}
+			else
+			{
+				glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
+				glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
+				glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer_offset);
+			}
+			idx_buffer_offset += pcmd->ElemCount;
+		}
+	}
+
+	// Restore modified GL state
+	glUseProgram(last_program);
+	glBindTexture(GL_TEXTURE_2D, last_texture);
+	glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, last_element_array_buffer);
+	glBindVertexArray(last_vertex_array);
+	glBlendEquationSeparate(last_blend_equation_rgb, last_blend_equation_alpha);
+	glBlendFunc(last_blend_src, last_blend_dst);
+	if (last_enable_blend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
+	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);
+}
+
+static const char* ImGui_ImplSdlOgl3_GetClipboardText()
+{
+	return SDL_GetClipboardText();
+}
+
+static void ImGui_ImplSdlOgl3_SetClipboardText(const char* text)
+{
+	SDL_SetClipboardText(text);
+}
+
+bool ImGui_ImplSdlOgl3_ProcessEvent(SDL_Event* event)
+{
+	ImGuiIO& io = ImGui::GetIO();
+	switch (event->type)
+	{
+	case SDL_MOUSEWHEEL:
+	{
+		if (event->wheel.y > 0)
+			g_MouseWheel = 1;
+		if (event->wheel.y < 0)
+			g_MouseWheel = -1;
+		return true;
+	}
+	case SDL_MOUSEBUTTONDOWN:
+	{
+		if (event->button.button == SDL_BUTTON_LEFT) g_MousePressed[0] = true;
+		if (event->button.button == SDL_BUTTON_RIGHT) g_MousePressed[1] = true;
+		if (event->button.button == SDL_BUTTON_MIDDLE) g_MousePressed[2] = true;
+		return true;
+	}
+	case SDL_TEXTINPUT:
+	{
+		ImGuiIO& io = ImGui::GetIO();
+		io.AddInputCharactersUTF8(event->text.text);
+		return true;
+	}
+	case SDL_KEYDOWN:
+	case SDL_KEYUP:
+	{
+		int key = event->key.keysym.sym & ~SDLK_SCANCODE_MASK;
+		io.KeysDown[key] = (event->type == SDL_KEYDOWN);
+		io.KeyShift = ((SDL_GetModState() & KMOD_SHIFT) != 0);
+		io.KeyCtrl = ((SDL_GetModState() & KMOD_CTRL) != 0);
+		io.KeyAlt = ((SDL_GetModState() & KMOD_ALT) != 0);
+		return true;
+	}
+	}
+	return false;
+}
+
+void ImGui_ImplSdlOgl3_CreateFontsTexture()
+{
+	ImGuiIO& io = ImGui::GetIO();
+
+	// Build texture atlas
+	unsigned char* pixels;
+	int width, height;
+	io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bits for OpenGL3 demo because it is more likely to be compatible with user's existing shader.
+
+															  // Create OpenGL texture
+	glGenTextures(1, &g_FontTexture);
+	glBindTexture(GL_TEXTURE_2D, g_FontTexture);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
+
+	// Store our identifier
+	io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;
+
+	// Cleanup (don't clear the input data if you want to append new fonts later)
+	io.Fonts->ClearInputData();
+	io.Fonts->ClearTexData();
+}
+
+bool ImGui_ImplSdlOgl3_CreateDeviceObjects()
+{
+	// Backup GL state
+	GLint last_texture, last_array_buffer, last_vertex_array;
+	glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
+	glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
+	glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
+
+	const GLchar *vertex_shader =
+		"#version 330\n"
+		"uniform mat4 ProjMtx;\n"
+		"in vec2 Position;\n"
+		"in vec2 UV;\n"
+		"in vec4 Color;\n"
+		"out vec2 Frag_UV;\n"
+		"out 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* fragment_shader =
+		"#version 330\n"
+		"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"
+		"}\n";
+
+	g_ShaderHandle = glCreateProgram();
+	g_VertHandle = glCreateShader(GL_VERTEX_SHADER);
+	g_FragHandle = glCreateShader(GL_FRAGMENT_SHADER);
+	glShaderSource(g_VertHandle, 1, &vertex_shader, 0);
+	glShaderSource(g_FragHandle, 1, &fragment_shader, 0);
+	glCompileShader(g_VertHandle);
+	glCompileShader(g_FragHandle);
+	glAttachShader(g_ShaderHandle, g_VertHandle);
+	glAttachShader(g_ShaderHandle, g_FragHandle);
+	glLinkProgram(g_ShaderHandle);
+
+	g_AttribLocationTex = glGetUniformLocation(g_ShaderHandle, "Texture");
+	g_AttribLocationProjMtx = glGetUniformLocation(g_ShaderHandle, "ProjMtx");
+	g_AttribLocationPosition = glGetAttribLocation(g_ShaderHandle, "Position");
+	g_AttribLocationUV = glGetAttribLocation(g_ShaderHandle, "UV");
+	g_AttribLocationColor = glGetAttribLocation(g_ShaderHandle, "Color");
+
+	glGenBuffers(1, &g_VboHandle);
+	glGenBuffers(1, &g_ElementsHandle);
+
+	glGenVertexArrays(1, &g_VaoHandle);
+	glBindVertexArray(g_VaoHandle);
+	glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
+	glEnableVertexAttribArray(g_AttribLocationPosition);
+	glEnableVertexAttribArray(g_AttribLocationUV);
+	glEnableVertexAttribArray(g_AttribLocationColor);
+
+#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
+	glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
+	glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
+	glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
+#undef OFFSETOF
+
+	ImGui_ImplSdlOgl3_CreateFontsTexture();
+
+	// Restore modified GL state
+	glBindTexture(GL_TEXTURE_2D, last_texture);
+	glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
+	glBindVertexArray(last_vertex_array);
+
+	return true;
+}
+
+void    ImGui_ImplSdlOgl3_InvalidateDeviceObjects()
+{
+	if (g_FontTexture)
+	{
+		glDeleteTextures(1, &g_FontTexture);
+		ImGui::GetIO().Fonts->TexID = 0;
+		g_FontTexture = 0;
+	}
+}
+
+bool    ImGui_ImplSdlOgl3_Init(SDL_Window *window)
+{
+	g_Window = window;
+
+	ImGuiIO& io = ImGui::GetIO();
+	io.KeyMap[ImGuiKey_Tab] = SDLK_TAB;                     // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
+	io.KeyMap[ImGuiKey_LeftArrow] = SDL_SCANCODE_LEFT;
+	io.KeyMap[ImGuiKey_RightArrow] = SDL_SCANCODE_RIGHT;
+	io.KeyMap[ImGuiKey_UpArrow] = SDL_SCANCODE_UP;
+	io.KeyMap[ImGuiKey_DownArrow] = SDL_SCANCODE_DOWN;
+	io.KeyMap[ImGuiKey_PageUp] = SDL_SCANCODE_PAGEUP;
+	io.KeyMap[ImGuiKey_PageDown] = SDL_SCANCODE_PAGEDOWN;
+	io.KeyMap[ImGuiKey_Home] = SDL_SCANCODE_HOME;
+	io.KeyMap[ImGuiKey_End] = SDL_SCANCODE_END;
+	io.KeyMap[ImGuiKey_Delete] = SDLK_DELETE;
+	io.KeyMap[ImGuiKey_Backspace] = SDLK_BACKSPACE;
+	io.KeyMap[ImGuiKey_Enter] = SDLK_RETURN;
+	io.KeyMap[ImGuiKey_Escape] = SDLK_ESCAPE;
+	io.KeyMap[ImGuiKey_A] = SDLK_a;
+	io.KeyMap[ImGuiKey_C] = SDLK_c;
+	io.KeyMap[ImGuiKey_V] = SDLK_v;
+	io.KeyMap[ImGuiKey_X] = SDLK_x;
+	io.KeyMap[ImGuiKey_Y] = SDLK_y;
+	io.KeyMap[ImGuiKey_Z] = SDLK_z;
+
+	io.RenderDrawListsFn = ImGui_ImplSdlOgl3_RenderDrawLists;   // Alternatively you can set this to NULL and call ImGui::GetDrawData() after ImGui::Render() to get the same ImDrawData pointer.
+	io.SetClipboardTextFn = ImGui_ImplSdlOgl3_SetClipboardText;
+	io.GetClipboardTextFn = ImGui_ImplSdlOgl3_GetClipboardText;
+
+#ifdef _WIN32
+	SDL_SysWMinfo wmInfo;
+	SDL_VERSION(&wmInfo.version);
+	SDL_GetWindowWMInfo(window, &wmInfo);
+	io.ImeWindowHandle = wmInfo.info.win.window;
+#endif
+
+	return true;
+}
+
+void ImGui_ImplSdlOgl3_Shutdown()
+{
+	if (g_VaoHandle) glDeleteVertexArrays(1, &g_VaoHandle);
+	if (g_VboHandle) glDeleteBuffers(1, &g_VboHandle);
+	if (g_ElementsHandle) glDeleteBuffers(1, &g_ElementsHandle);
+	g_VaoHandle = g_VboHandle = g_ElementsHandle = 0;
+
+	glDetachShader(g_ShaderHandle, g_VertHandle);
+	glDeleteShader(g_VertHandle);
+	g_VertHandle = 0;
+
+	glDetachShader(g_ShaderHandle, g_FragHandle);
+	glDeleteShader(g_FragHandle);
+	g_FragHandle = 0;
+
+	glDeleteProgram(g_ShaderHandle);
+	g_ShaderHandle = 0;
+
+	if (g_FontTexture)
+	{
+		glDeleteTextures(1, &g_FontTexture);
+		ImGui::GetIO().Fonts->TexID = 0;
+		g_FontTexture = 0;
+	}
+	ImGui::Shutdown();
+}
+
+void ImGui_ImplSdlOgl3_NewFrame(SDL_Window *window)
+{
+	if (!g_FontTexture)
+		ImGui_ImplSdlOgl3_CreateDeviceObjects();
+
+	ImGuiIO& io = ImGui::GetIO();
+
+	// Setup display size (every frame to accommodate for window resizing)
+	int w, h;
+	int display_w, display_h;
+	SDL_GetWindowSize(window, &w, &h);
+	SDL_GetWindowSize(window, &display_w, &display_h);
+	io.DisplaySize = ImVec2((float)w, (float)h);
+	io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);
+
+	// Setup time step
+	Uint32	time = SDL_GetTicks();
+	double current_time = time / 1000.0;
+	io.DeltaTime = g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f / 60.0f);
+	g_Time = current_time;
+
+	// Setup inputs
+	// (we already got mouse wheel, keyboard keys & characters from glfw callbacks polled in glfwPollEvents())
+	int mx, my;
+	Uint32 mouseMask = SDL_GetMouseState(&mx, &my);
+	if (SDL_GetWindowFlags(window) & SDL_WINDOW_MOUSE_FOCUS)
+		io.MousePos = ImVec2((float)mx, (float)my);   // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
+	else
+		io.MousePos = ImVec2(-1, -1);
+
+	io.MouseDown[0] = g_MousePressed[0] || (mouseMask & SDL_BUTTON(SDL_BUTTON_LEFT)) != 0;		// If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
+	io.MouseDown[1] = g_MousePressed[1] || (mouseMask & SDL_BUTTON(SDL_BUTTON_RIGHT)) != 0;
+	io.MouseDown[2] = g_MousePressed[2] || (mouseMask & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
+	g_MousePressed[0] = g_MousePressed[1] = g_MousePressed[2] = false;
+
+	io.MouseWheel = g_MouseWheel;
+	g_MouseWheel = 0.0f;
+
+	// Hide OS mouse cursor if ImGui is drawing it
+	SDL_ShowCursor(io.MouseDrawCursor ? 0 : 1);
+
+	// Start the frame
+	ImGui::NewFrame();
+}