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adding NanoVG example (not included in CMake, requires NanoVG libs)
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demos/nanovg/main.c
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demos/nanovg/main.c
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#include <SDL2/SDL.h>
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#include <SDL2/SDL_gpu.h>
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#define GLEW_STATIC // needed for windows only(?)
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#include <GL/glew.h>
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#define NANOVG_GL3_IMPLEMENTATION
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#include "nanovg/nanovg.h"
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#include "nanovg/nanovg_gl.h"
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#include "nanovg/nanovg_gl_utils.h"
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/* Create a GPU_Image from a NanoVG Framebuffer */
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GPU_Image* generateFBO(NVGcontext* _vg, const float _w, const float _h, void (*draw)(NVGcontext*, const float, const float, const float, const float)) {
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// GPU_FlushBlitBuffer(); // you may want to call this if you're doing this in the middle of SDL_gpu blitting
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NVGLUframebuffer* fb = nvgluCreateFramebuffer(_vg, _w, _h, 0); // IMPORTANT: don't run nvgluDeleteFramebuffer
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nvgluBindFramebuffer(fb);
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glViewport(0, 0, _w, _h);
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glClearColor(0, 0, 0, 0);
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glClear(GL_COLOR_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);
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nvgBeginFrame(_vg, _w, _h, 1.0f);
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draw(_vg, 0, 0, _w, _h); // call the drawing function that was passed as parameter
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nvgEndFrame(_vg);
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/* nvgluBindFramebuffer(0); // official documentation says to unbind, but I haven't had issues not doing it */
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GPU_ResetRendererState(); // not calling GPU_ResetRendererState can cause problems with SDL_gpu depending on your order of operations
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// IMPORTANT: don't run nvgluDeleteFramebuffer, GPU_CreateImageUsingTexture takes the handle
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return GPU_CreateImageUsingTexture(fb->texture, false); // should take_ownership be true?
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}
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/* Simple Drawing Example */
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void drawNVG(NVGcontext* _vg, const float _x, const float _y, const float _w, const float _h) {
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const float square_r = 5.0f;
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nvgBeginPath(_vg);
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nvgRoundedRect(_vg, _x, _y, _w, _h, square_r);
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NVGpaint bg_paint = nvgLinearGradient(_vg, _x, _y, _x+_w, _y+_h, nvgRGBA(255, 255, 255, 255), nvgRGBA(255, 255, 255, 155));
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nvgFillPaint(_vg, bg_paint);
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nvgFill(_vg);
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}
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/* draw something that takes some awhile */
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void drawComplexNVG(NVGcontext* _vg, const float _x, const float _y, const float _w, const float _h) {
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float x = _x;
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float y = _y;
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nvgBeginPath(_vg);
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nvgMoveTo(_vg, x, y);
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for (unsigned i = 1; i < 50000; i++) {
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nvgBezierTo(_vg, x-10.0f, y+10.0f, x+25, y+25, x,y);
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x += 10.0f;
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y += 5.0f;
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if (x > _w)
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x = 0.0f;
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if (y > _h)
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y = 0.0f;
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}
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NVGpaint stroke_paint = nvgLinearGradient(_vg, _x, _y, _w, _h, nvgRGBA(255, 255, 255, 20), nvgRGBA(0, 255, 255, 10));
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nvgStrokePaint(_vg, stroke_paint);
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nvgStroke(_vg);
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}
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/* Can help show STENCIL problems when _arc_radius because concave (convex?) */
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void drawPie(NVGcontext* _vg, const float _x, const float _y, const float _arc_radius) {
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const float pie_radius = 100.0f;
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nvgBeginPath(_vg);
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nvgMoveTo(_vg, _x, _y);
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nvgArc(_vg, _x, _y, pie_radius, 0.0f, nvgDegToRad(_arc_radius), NVG_CW);
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nvgLineTo(_vg, _x, _y);
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nvgFillColor(_vg, nvgRGBA(0xFF,0xFF,0xFF,0xFF));
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nvgFill(_vg);
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}
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void main_loop(GPU_Target* _screen, NVGcontext* _vg, const Uint16 _screen_w, const Uint16 _screen_h) {
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const float px_ratio = (float)_screen_w / (float)_screen_w; // spoilers: it's 1.0f
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GPU_Rect fbo_simple_rect = { 65.0f, 10.0f, 50.0f, 50.0f}; // Blitting Destination
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GPU_Image* fbo_simple = generateFBO(_vg, fbo_simple_rect.w, fbo_simple_rect.h, drawNVG);
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GPU_Rect fbo_complex_rect = { 0.0f, 0.0f, _screen_w, _screen_h}; // Blitting Destination
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GPU_Image* fbo_complex = generateFBO(_vg, fbo_complex_rect.w, fbo_complex_rect.h, drawComplexNVG);
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float arc_radius = 0.0f;
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SDL_Event event;
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bool loop = true;
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do {
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/* SDL Event Handling */
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while(SDL_PollEvent(&event)) {
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if(event.type == SDL_QUIT)
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loop = false;
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else if(event.type == SDL_KEYDOWN) {
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if(event.key.keysym.sym == SDLK_ESCAPE)
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loop = false;
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}
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}
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/* Animation Pass */
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arc_radius += 1.0f;
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/* SDL_gpu + NanoVG Rendering */
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GPU_ClearRGBA(_screen, 0x00, 0x00, 0x00, 0xFF); // GPU_ClearRGBA clears GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT
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glClear(GL_STENCIL_BUFFER_BIT); // IMPORTANT: GPU_ClearRGBA does not clear GL_STENCIL_BUFFER_BIT
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/* SDL_gpu Blitting */
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GPU_BlitRectX(fbo_complex, NULL, _screen, &fbo_complex_rect, 0.0f, 0.0f, 0.0f, GPU_FLIP_VERTICAL); // IMPORTANT: GPU_BlitRectX is required to use GPU_FLIP_VERTICAL which is required for NVGLUframebuffer data (why???)
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GPU_BlitRectX(fbo_simple, NULL, _screen, &fbo_simple_rect, 0.0f, 0.0f, 0.0f, GPU_FLIP_VERTICAL); // IMPORTANT: GPU_BlitRectX is required to use GPU_FLIP_VERTICAL which is required for NVGLUframebuffer data (why???)
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/* NanoVG Section */
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GPU_FlushBlitBuffer(); // IMPORTANT: run GPU_FlushBlitBuffer before nvgBeginFrame
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nvgBeginFrame(_vg, _screen_w, _screen_h, px_ratio); // Do your normal NanoVG stuff
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drawNVG(_vg, 10.0f, 10.0f, fbo_simple_rect.w, fbo_simple_rect.h); // run our simple drawing code directly
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drawPie(_vg, _screen_w/2, _screen_h/2, arc_radius); // drawing the pie chart will break if you don't have a stencil buffer
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/* drawComplexNVG(_vg); */
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nvgEndFrame(_vg); // Finish our NanoVG pass
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GPU_ResetRendererState(); // IMPORTANT: run GPU_ResetRendererState after nvgEndFrame
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/* Finish */
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GPU_Flip(_screen); // Render to screen
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} while (loop);
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/* Loops over, Cleanup */
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GPU_FreeImage(fbo_simple);
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GPU_FreeImage(fbo_complex);
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}
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int main() {
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const Uint16 screen_w = 500;
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const Uint16 screen_h = 500;
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/* Init SDL and our renderer, no error handling! */
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SDL_Init(SDL_INIT_EVERYTHING); // Init SDL
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SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 1); // NanoVG _REQUIRES_ a stencil buffer
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GPU_Target* target = GPU_InitRenderer(GPU_RENDERER_OPENGL_3, screen_w, screen_h, 0); // Init SDL_gpu
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NVGcontext* vg = nvgCreateGL3(NVG_ANTIALIAS | NVG_STENCIL_STROKES | NVG_DEBUG); // Init NanoVG
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main_loop(target, vg, screen_w, screen_h);
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return 0;
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}