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ShaderPlayground / deps / imgui / imgui / backends / imgui_impl_opengl2.cpp
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1// dear imgui: Renderer Backend for OpenGL2 (legacy OpenGL, fixed pipeline)
2// This needs to be used along with a Platform Backend (e.g. GLFW, SDL, Win32, custom..)
3
4// Implemented features:
5// [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture as texture identifier. Read the FAQ about ImTextureID/ImTextureRef!
6// [X] Renderer: Texture updates support for dynamic font atlas (ImGuiBackendFlags_RendererHasTextures).
7// [X] Renderer: Multi-viewport support (multiple windows). Enable with 'io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable'.
8// Missing features or Issues:
9// [ ] Renderer: Large meshes support (64k+ vertices) even with 16-bit indices (ImGuiBackendFlags_RendererHasVtxOffset).
10// [ ] Renderer: Use of DrawCallback_SetSamplerLinear, DrawCallback_SetSamplerNearest is emulated by poking to glTexParameter(), as legacy OpenGL doesn't have glBindSampler().
11
12// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
13// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
14// Learn about Dear ImGui:
15// - FAQ https://dearimgui.com/faq
16// - Getting Started https://dearimgui.com/getting-started
17// - Documentation https://dearimgui.com/docs (same as your local docs/ folder).
18// - Introduction, links and more at the top of imgui.cpp
19
20// **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
21// **Prefer using the code in imgui_impl_opengl3.cpp**
22// This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.
23// If your code is using GL3+ context or any semi modern OpenGL calls, using this is likely to make everything more
24// complicated, will require your code to reset every single OpenGL attributes to their initial state, and might
25// confuse your GPU driver.
26// The GL2 code is unable to reset attributes or even call e.g. "glUseProgram(0)" because they don't exist in that API.
27
28// CHANGELOG
29// (minor and older changes stripped away, please see git history for details)
30// 2026-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
31// 2026-04-23: OpenGL: Added support for standard draw callbacks (in platform_io): DrawCallback_ResetRenderState, DrawCallback_SetSamplerLinear, DrawCallback_SetSamplerNearest. (#9378)
32// 2026-03-12: OpenGL: Fixed invalid assert in ImGui_ImplOpenGL3_UpdateTexture() if ImTextureID_Invalid is defined to be != 0, which became the default since 2026-03-12. (#9295)
33// 2025-09-18: Call platform_io.ClearRendererHandlers() on shutdown.
34// 2025-07-15: OpenGL: Set GL_UNPACK_ALIGNMENT to 1 before updating textures. (#8802)
35// 2025-06-11: OpenGL: Added support for ImGuiBackendFlags_RendererHasTextures, for dynamic font atlas. Removed ImGui_ImplOpenGL2_CreateFontsTexture() and ImGui_ImplOpenGL2_DestroyFontsTexture().
36// 2024-10-07: OpenGL: Changed default texture sampler to Clamp instead of Repeat/Wrap.
37// 2024-06-28: OpenGL: ImGui_ImplOpenGL2_NewFrame() recreates font texture if it has been destroyed by ImGui_ImplOpenGL2_DestroyFontsTexture(). (#7748)
38// 2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
39// 2021-12-08: OpenGL: Fixed mishandling of the ImDrawCmd::IdxOffset field! This is an old bug but it never had an effect until some internal rendering changes in 1.86.
40// 2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
41// 2021-05-19: OpenGL: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
42// 2021-01-03: OpenGL: Backup, setup and restore GL_SHADE_MODEL state, disable GL_STENCIL_TEST and disable GL_NORMAL_ARRAY client state to increase compatibility with legacy OpenGL applications.
43// 2020-01-23: OpenGL: Backup, setup and restore GL_TEXTURE_ENV to increase compatibility with legacy OpenGL applications.
44// 2019-04-30: OpenGL: Added support for special ImDrawCallback_ResetRenderState callback to reset render state.
45// 2019-02-11: OpenGL: Projecting clipping rectangles correctly using draw_data->FramebufferScale to allow multi-viewports for retina display.
46// 2018-11-30: Misc: Setting up io.BackendRendererName so it can be displayed in the About Window.
47// 2018-08-03: OpenGL: Disabling/restoring GL_LIGHTING and GL_COLOR_MATERIAL to increase compatibility with legacy OpenGL applications.
48// 2018-06-08: Misc: Extracted imgui_impl_opengl2.cpp/.h away from the old combined GLFW/SDL+OpenGL2 examples.
49// 2018-06-08: OpenGL: Use draw_data->DisplayPos and draw_data->DisplaySize to setup projection matrix and clipping rectangle.
50// 2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplOpenGL2_RenderDrawData() in the .h file so you can call it yourself.
51// 2017-09-01: OpenGL: Save and restore current polygon mode.
52// 2016-09-10: OpenGL: Uploading font texture as RGBA32 to increase compatibility with users shaders (not ideal).
53// 2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
54
55#include "imgui.h"
56#ifndef IMGUI_DISABLE
57#include "imgui_impl_opengl2.h"
58#include <stdint.h> // intptr_t
59
60// Clang/GCC warnings with -Weverything
61#if defined(__clang__)
62#pragma clang diagnostic push
63#pragma clang diagnostic ignored "-Wunused-macros" // warning: macro is not used
64#pragma clang diagnostic ignored "-Wnonportable-system-include-path"
65#endif
66
67// Include OpenGL header (without an OpenGL loader) requires a bit of fiddling
68#if defined(_WIN32) && !defined(APIENTRY)
69#define APIENTRY __stdcall // It is customary to use APIENTRY for OpenGL function pointer declarations on all platforms. Additionally, the Windows OpenGL header needs APIENTRY.
70#endif
71#if defined(_WIN32) && !defined(WINGDIAPI)
72#define WINGDIAPI __declspec(dllimport) // Some Windows OpenGL headers need this
73#endif
74#if defined(__APPLE__)
75#define GL_SILENCE_DEPRECATION
76#include <OpenGL/gl.h>
77#else
78#include <GL/gl.h>
79#endif
80
81// [Debugging]
82//#define IMGUI_IMPL_OPENGL_DEBUG
83#ifdef IMGUI_IMPL_OPENGL_DEBUG
84#include <stdio.h>
85#define GL_CALL(_CALL) do { _CALL; GLenum gl_err = glGetError(); if (gl_err != 0) fprintf(stderr, "GL error 0x%x returned from '%s'.\n", gl_err, #_CALL); } while (0) // Call with error check
86#else
87#define GL_CALL(_CALL) _CALL // Call without error check
88#endif
89
90// OpenGL data
91struct ImGui_ImplOpenGL2_Data
92{
93 bool UseTexParameterToSetSampler;
94 GLuint NextSampler;
95
96 ImGui_ImplOpenGL2_Data() { memset((void*)this, 0, sizeof(*this)); }
97};
98
99// Backend data stored in io.BackendRendererUserData to allow support for multiple Dear ImGui contexts
100// It is STRONGLY preferred that you use docking branch with multi-viewports (== single Dear ImGui context + multiple windows) instead of multiple Dear ImGui contexts.
101static ImGui_ImplOpenGL2_Data* ImGui_ImplOpenGL2_GetBackendData()
102{
103 return ImGui::GetCurrentContext() ? (ImGui_ImplOpenGL2_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;
104}
105
106// Forward Declarations
107static void ImGui_ImplOpenGL2_InitMultiViewportSupport();
108static void ImGui_ImplOpenGL2_ShutdownMultiViewportSupport();
109
110// Functions
111void ImGui_ImplOpenGL2_NewFrame()
112{
113 ImGui_ImplOpenGL2_Data* bd = ImGui_ImplOpenGL2_GetBackendData();
114 IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplOpenGL2_Init()?");
115 IM_UNUSED(bd);
116}
117
118static void ImGui_ImplOpenGL2_SetupRenderState(ImDrawData* draw_data, int fb_width, int fb_height)
119{
120 // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers, polygon fill.
121 ImGui_ImplOpenGL2_Data* bd = ImGui_ImplOpenGL2_GetBackendData();
122 glEnable(GL_BLEND);
123 glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
124 //glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA); // In order to composite our output buffer we need to preserve alpha
125 glDisable(GL_CULL_FACE);
126 glDisable(GL_DEPTH_TEST);
127 glDisable(GL_STENCIL_TEST);
128 glDisable(GL_LIGHTING);
129 glDisable(GL_COLOR_MATERIAL);
130 glEnable(GL_SCISSOR_TEST);
131 glEnableClientState(GL_VERTEX_ARRAY);
132 glEnableClientState(GL_TEXTURE_COORD_ARRAY);
133 glEnableClientState(GL_COLOR_ARRAY);
134 glDisableClientState(GL_NORMAL_ARRAY);
135 glEnable(GL_TEXTURE_2D);
136 glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
137 glShadeModel(GL_SMOOTH);
138 glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
139 bd->NextSampler = GL_LINEAR;
140
141 // If you are using this code with non-legacy OpenGL header/contexts (which you should not, prefer using imgui_impl_opengl3.cpp!!),
142 // you may need to backup/reset/restore other state, e.g. for current shader using the commented lines below.
143 // (DO NOT MODIFY THIS FILE! Add the code in your calling function)
144 // GLint last_program;
145 // glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
146 // glUseProgram(0);
147 // ImGui_ImplOpenGL2_RenderDrawData(...);
148 // glUseProgram(last_program)
149 // There are potentially many more states you could need to clear/setup that we can't access from default headers.
150 // e.g. glBindBuffer(GL_ARRAY_BUFFER, 0), glDisable(GL_TEXTURE_CUBE_MAP).
151
152 // Setup viewport, orthographic projection matrix
153 // Our visible imgui space lies from draw_data->DisplayPos (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayPos is (0,0) for single viewport apps.
154 GL_CALL(glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height));
155 glMatrixMode(GL_PROJECTION);
156 glPushMatrix();
157 glLoadIdentity();
158 glOrtho(draw_data->DisplayPos.x, draw_data->DisplayPos.x + draw_data->DisplaySize.x, draw_data->DisplayPos.y + draw_data->DisplaySize.y, draw_data->DisplayPos.y, -1.0f, +1.0f);
159 glMatrixMode(GL_MODELVIEW);
160 glPushMatrix();
161 glLoadIdentity();
162}
163
164// Draw callbacks
165static void ImGui_ImplOpenGL2_DrawCallback_ResetRenderState(const ImDrawList*, const ImDrawCmd*) {} // Intentionally empty. Used as an identifier for rendering loop to call its code. Simpler to implement this way.
166static void ImGui_ImplOpenGL2_DrawCallback_SetSamplerLinear(const ImDrawList*, const ImDrawCmd*) { ImGui_ImplOpenGL2_Data* bd = ImGui_ImplOpenGL2_GetBackendData(); bd->UseTexParameterToSetSampler = true; bd->NextSampler = GL_LINEAR; }
167static void ImGui_ImplOpenGL2_DrawCallback_SetSamplerNearest(const ImDrawList*, const ImDrawCmd*) { ImGui_ImplOpenGL2_Data* bd = ImGui_ImplOpenGL2_GetBackendData(); bd->UseTexParameterToSetSampler = true; bd->NextSampler = GL_NEAREST; }
168
169// OpenGL2 Render function.
170// Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly.
171// This is in order to be able to run within an OpenGL engine that doesn't do so.
172void ImGui_ImplOpenGL2_RenderDrawData(ImDrawData* draw_data)
173{
174 // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
175 ImGui_ImplOpenGL2_Data* bd = ImGui_ImplOpenGL2_GetBackendData();
176 int fb_width = (int)(draw_data->DisplaySize.x * draw_data->FramebufferScale.x);
177 int fb_height = (int)(draw_data->DisplaySize.y * draw_data->FramebufferScale.y);
178 if (fb_width == 0 || fb_height == 0)
179 return;
180
181 // Catch up with texture updates. Most of the times, the list will have 1 element with an OK status, aka nothing to do.
182 // (This almost always points to ImGui::GetPlatformIO().Textures[] but is part of ImDrawData to allow overriding or disabling texture updates).
183 if (draw_data->Textures != nullptr)
184 for (ImTextureData* tex : *draw_data->Textures)
185 if (tex->Status != ImTextureStatus_OK)
186 ImGui_ImplOpenGL2_UpdateTexture(tex);
187
188 // Backup GL state
189 GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
190 GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
191 GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
192 GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
193 GLint last_shade_model; glGetIntegerv(GL_SHADE_MODEL, &last_shade_model);
194 GLint last_tex_env_mode; glGetTexEnviv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, &last_tex_env_mode);
195 glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
196
197 // Setup desired GL state
198 ImGui_ImplOpenGL2_SetupRenderState(draw_data, fb_width, fb_height);
199
200 // Will project scissor/clipping rectangles into framebuffer space
201 ImVec2 clip_off = draw_data->DisplayPos; // (0,0) unless using multi-viewports
202 ImVec2 clip_scale = draw_data->FramebufferScale; // (1,1) unless using retina display which are often (2,2)
203
204 // Render command lists
205 for (const ImDrawList* draw_list : draw_data->CmdLists)
206 {
207 const ImDrawVert* vtx_buffer = draw_list->VtxBuffer.Data;
208 const ImDrawIdx* idx_buffer = draw_list->IdxBuffer.Data;
209 glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + offsetof(ImDrawVert, pos)));
210 glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + offsetof(ImDrawVert, uv)));
211 glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + offsetof(ImDrawVert, col)));
212
213 for (int cmd_i = 0; cmd_i < draw_list->CmdBuffer.Size; cmd_i++)
214 {
215 const ImDrawCmd* pcmd = &draw_list->CmdBuffer[cmd_i];
216 if (pcmd->UserCallback)
217 {
218 // User callback, registered via ImDrawList::AddCallback()
219 if (pcmd->UserCallback == ImGui_ImplOpenGL2_DrawCallback_ResetRenderState)
220 ImGui_ImplOpenGL2_SetupRenderState(draw_data, fb_width, fb_height);
221 else
222 pcmd->UserCallback(draw_list, pcmd);
223 }
224 else
225 {
226 // Project scissor/clipping rectangles into framebuffer space
227 ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);
228 ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y);
229 if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)
230 continue;
231
232 // Apply scissor/clipping rectangle (Y is inverted in OpenGL)
233 glScissor((int)clip_min.x, (int)((float)fb_height - clip_max.y), (int)(clip_max.x - clip_min.x), (int)(clip_max.y - clip_min.y));
234
235 // Bind texture, Draw
236 GLuint pcmd_texture = (GLuint)(intptr_t)pcmd->GetTexID();
237 glBindTexture(GL_TEXTURE_2D, pcmd_texture);
238
239 // Emulate sampler change (even though it is technically part of texture data)
240 // As a sort of hack/workaround, we only start writing using glTextParameter() if sampler is ever changed explicitly.
241 if (bd->UseTexParameterToSetSampler)
242 {
243 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, bd->NextSampler);
244 glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, bd->NextSampler);
245 }
246
247 glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer + pcmd->IdxOffset);
248 }
249 }
250 }
251
252 // Restore modified GL state
253 glDisableClientState(GL_COLOR_ARRAY);
254 glDisableClientState(GL_TEXTURE_COORD_ARRAY);
255 glDisableClientState(GL_VERTEX_ARRAY);
256 glBindTexture(GL_TEXTURE_2D, (GLuint)last_texture);
257 glMatrixMode(GL_MODELVIEW);
258 glPopMatrix();
259 glMatrixMode(GL_PROJECTION);
260 glPopMatrix();
261 glPopAttrib();
262 glPolygonMode(GL_FRONT, (GLenum)last_polygon_mode[0]); glPolygonMode(GL_BACK, (GLenum)last_polygon_mode[1]);
263 glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
264 glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
265 glShadeModel(last_shade_model);
266 glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, last_tex_env_mode);
267}
268
269void ImGui_ImplOpenGL2_UpdateTexture(ImTextureData* tex)
270{
271 if (tex->Status == ImTextureStatus_WantCreate)
272 {
273 // Create and upload new texture to graphics system
274 //IMGUI_DEBUG_LOG("UpdateTexture #%03d: WantCreate %dx%d\n", tex->UniqueID, tex->Width, tex->Height);
275 IM_ASSERT(tex->TexID == ImTextureID_Invalid && tex->BackendUserData == nullptr);
276 IM_ASSERT(tex->Format == ImTextureFormat_RGBA32);
277 const void* pixels = tex->GetPixels();
278 GLuint gl_texture_id = 0;
279
280 // Upload texture to graphics system
281 // (Bilinear sampling is required by default. Set 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines' or 'style.AntiAliasedLinesUseTex = false' to allow point/nearest sampling)
282 GLint last_texture;
283 GL_CALL(glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture));
284 GL_CALL(glGenTextures(1, &gl_texture_id));
285 GL_CALL(glBindTexture(GL_TEXTURE_2D, gl_texture_id));
286 GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR));
287 GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR));
288 GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP));
289 GL_CALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP));
290 GL_CALL(glPixelStorei(GL_UNPACK_ROW_LENGTH, 0));
291 GL_CALL(glPixelStorei(GL_UNPACK_ALIGNMENT, 1));
292 GL_CALL(glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex->Width, tex->Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels));
293
294 // Store identifiers
295 tex->SetTexID((ImTextureID)(intptr_t)gl_texture_id);
296 tex->SetStatus(ImTextureStatus_OK);
297
298 // Restore state
299 GL_CALL(glBindTexture(GL_TEXTURE_2D, last_texture));
300 }
301 else if (tex->Status == ImTextureStatus_WantUpdates)
302 {
303 // Update selected blocks. We only ever write to textures regions which have never been used before!
304 // This backend choose to use tex->Updates[] but you can use tex->UpdateRect to upload a single region.
305 GLint last_texture;
306 GL_CALL(glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture));
307
308 GLuint gl_tex_id = (GLuint)(intptr_t)tex->TexID;
309 GL_CALL(glBindTexture(GL_TEXTURE_2D, gl_tex_id));
310 GL_CALL(glPixelStorei(GL_UNPACK_ROW_LENGTH, tex->Width));
311 GL_CALL(glPixelStorei(GL_UNPACK_ALIGNMENT, 1));
312 for (ImTextureRect& r : tex->Updates)
313 GL_CALL(glTexSubImage2D(GL_TEXTURE_2D, 0, r.x, r.y, r.w, r.h, GL_RGBA, GL_UNSIGNED_BYTE, tex->GetPixelsAt(r.x, r.y)));
314 GL_CALL(glPixelStorei(GL_UNPACK_ROW_LENGTH, 0));
315 GL_CALL(glBindTexture(GL_TEXTURE_2D, last_texture)); // Restore state
316 tex->SetStatus(ImTextureStatus_OK);
317 }
318 else if (tex->Status == ImTextureStatus_WantDestroy)
319 {
320 GLuint gl_tex_id = (GLuint)(intptr_t)tex->TexID;
321 glDeleteTextures(1, &gl_tex_id);
322
323 // Clear identifiers and mark as destroyed (in order to allow e.g. calling InvalidateDeviceObjects while running)
324 tex->SetTexID(ImTextureID_Invalid);
325 tex->SetStatus(ImTextureStatus_Destroyed);
326 }
327}
328
329bool ImGui_ImplOpenGL2_CreateDeviceObjects()
330{
331 return true;
332}
333
334void ImGui_ImplOpenGL2_DestroyDeviceObjects()
335{
336 for (ImTextureData* tex : ImGui::GetPlatformIO().Textures)
337 if (tex->RefCount == 1)
338 {
339 tex->SetStatus(ImTextureStatus_WantDestroy);
340 ImGui_ImplOpenGL2_UpdateTexture(tex);
341 }
342}
343
344bool ImGui_ImplOpenGL2_Init()
345{
346 ImGuiIO& io = ImGui::GetIO();
347 IMGUI_CHECKVERSION();
348 IM_ASSERT(io.BackendRendererUserData == nullptr && "Already initialized a renderer backend!");
349
350 // Setup backend capabilities flags
351 ImGui_ImplOpenGL2_Data* bd = IM_NEW(ImGui_ImplOpenGL2_Data)();
352 io.BackendRendererUserData = (void*)bd;
353 io.BackendRendererName = "imgui_impl_opengl2";
354 io.BackendFlags |= ImGuiBackendFlags_RendererHasTextures; // We can honor ImGuiPlatformIO::Textures[] requests during render.
355 io.BackendFlags |= ImGuiBackendFlags_RendererHasViewports; // We can create multi-viewports on the Renderer side (optional)
356
357 ImGui_ImplOpenGL2_InitMultiViewportSupport();
358
359 ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
360 platform_io.DrawCallback_ResetRenderState = ImGui_ImplOpenGL2_DrawCallback_ResetRenderState;
361 platform_io.DrawCallback_SetSamplerLinear = ImGui_ImplOpenGL2_DrawCallback_SetSamplerLinear;
362 platform_io.DrawCallback_SetSamplerNearest = ImGui_ImplOpenGL2_DrawCallback_SetSamplerNearest;
363
364 return true;
365}
366
367void ImGui_ImplOpenGL2_Shutdown()
368{
369 ImGui_ImplOpenGL2_Data* bd = ImGui_ImplOpenGL2_GetBackendData();
370 IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
371 ImGuiIO& io = ImGui::GetIO();
372 ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
373
374 ImGui_ImplOpenGL2_ShutdownMultiViewportSupport();
375 ImGui_ImplOpenGL2_DestroyDeviceObjects();
376
377 io.BackendRendererName = nullptr;
378 io.BackendRendererUserData = nullptr;
379 io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasTextures | ImGuiBackendFlags_RendererHasViewports);
380 platform_io.ClearRendererHandlers();
381 IM_DELETE(bd);
382}
383
384//--------------------------------------------------------------------------------------------------------
385// MULTI-VIEWPORT / PLATFORM INTERFACE SUPPORT
386// This is an _advanced_ and _optional_ feature, allowing the backend to create and handle multiple viewports simultaneously.
387// If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
388//--------------------------------------------------------------------------------------------------------
389
390static void ImGui_ImplOpenGL2_RenderWindow(ImGuiViewport* viewport, void*)
391{
392 if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
393 {
394 ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
395 glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
396 glClear(GL_COLOR_BUFFER_BIT);
397 }
398 ImGui_ImplOpenGL2_RenderDrawData(viewport->DrawData);
399}
400
401static void ImGui_ImplOpenGL2_InitMultiViewportSupport()
402{
403 ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
404 platform_io.Renderer_RenderWindow = ImGui_ImplOpenGL2_RenderWindow;
405}
406
407static void ImGui_ImplOpenGL2_ShutdownMultiViewportSupport()
408{
409 ImGui::DestroyPlatformWindows();
410}
411
412//-----------------------------------------------------------------------------
413
414#if defined(__clang__)
415#pragma clang diagnostic pop
416#endif
417
418#endif // #ifndef IMGUI_DISABLE