mirror of
https://github.com/Relintai/sdl2_frt.git
synced 2025-03-21 02:12:27 +01:00
24c86b5501
since the window system doesn't do it for us like other platforms. This prevents sticky keys and missed keys when going in and out of focus, for example Alt would appear to stick if switching away from an SDL app with Alt-Tab and had to be pressed again. CR: Sam
126 lines
3.8 KiB
C
126 lines
3.8 KiB
C
/*
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* touch.c
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* written by Holmes Futrell
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* use however you want
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*/
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#include "SDL.h"
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#include "math.h"
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#include "common.h"
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#define BRUSH_SIZE 32 /* width and height of the brush */
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#define PIXELS_PER_ITERATION 5 /* number of pixels between brush blots when forming a line */
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static SDL_Texture *brush = 0; /* texture for the brush */
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/*
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draws a line from (startx, starty) to (startx + dx, starty + dy)
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this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart
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*/
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void
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drawLine(SDL_Renderer *renderer, float startx, float starty, float dx, float dy)
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{
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float distance = sqrt(dx * dx + dy * dy); /* length of line segment (pythagoras) */
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int iterations = distance / PIXELS_PER_ITERATION + 1; /* number of brush sprites to draw for the line */
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float dx_prime = dx / iterations; /* x-shift per iteration */
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float dy_prime = dy / iterations; /* y-shift per iteration */
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SDL_Rect dstRect; /* rect to draw brush sprite into */
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dstRect.w = BRUSH_SIZE;
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dstRect.h = BRUSH_SIZE;
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/* setup x and y for the location of the first sprite */
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float x = startx - BRUSH_SIZE / 2.0f;
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float y = starty - BRUSH_SIZE / 2.0f;
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int i;
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/* draw a series of blots to form the line */
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for (i = 0; i < iterations; i++) {
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dstRect.x = x;
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dstRect.y = y;
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/* shift x and y for next sprite location */
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x += dx_prime;
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y += dy_prime;
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/* draw brush blot */
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SDL_RenderCopy(renderer, brush, NULL, &dstRect);
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}
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}
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/*
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loads the brush texture
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*/
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void
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initializeTexture(SDL_Renderer *renderer)
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{
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SDL_Surface *bmp_surface;
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bmp_surface = SDL_LoadBMP("stroke.bmp");
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if (bmp_surface == NULL) {
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fatalError("could not load stroke.bmp");
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}
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brush =
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SDL_CreateTextureFromSurface(renderer, bmp_surface);
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SDL_FreeSurface(bmp_surface);
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if (brush == 0) {
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fatalError("could not create brush texture");
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}
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/* additive blending -- laying strokes on top of eachother makes them brighter */
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SDL_SetTextureBlendMode(brush, SDL_BLENDMODE_ADD);
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/* set brush color (red) */
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SDL_SetTextureColorMod(brush, 255, 100, 100);
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}
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int
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main(int argc, char *argv[])
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{
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int x, y, dx, dy; /* mouse location */
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Uint8 state; /* mouse (touch) state */
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SDL_Event event;
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SDL_Window *window; /* main window */
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SDL_Renderer *renderer;
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int done; /* does user want to quit? */
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/* initialize SDL */
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if (SDL_Init(SDL_INIT_VIDEO) < 0) {
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fatalError("Could not initialize SDL");
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}
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/* create main window and renderer */
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window = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,
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SDL_WINDOW_OPENGL |
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SDL_WINDOW_BORDERLESS);
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renderer = SDL_CreateRenderer(window, 0, 0);
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/* load brush texture */
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initializeTexture(renderer);
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/* fill canvass initially with all black */
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SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
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SDL_RenderClear(renderer);
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SDL_RenderPresent(renderer);
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done = 0;
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while (!done && SDL_WaitEvent(&event)) {
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switch (event.type) {
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case SDL_QUIT:
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done = 1;
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break;
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case SDL_MOUSEMOTION:
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state = SDL_GetMouseState(&x, &y); /* get its location */
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SDL_GetRelativeMouseState(&dx, &dy); /* find how much the mouse moved */
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if (state & SDL_BUTTON_LMASK) { /* is the mouse (touch) down? */
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drawLine(renderer, x - dx, y - dy, dx, dy); /* draw line segment */
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SDL_RenderPresent(renderer);
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}
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break;
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}
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}
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/* cleanup */
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SDL_DestroyTexture(brush);
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SDL_Quit();
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return 0;
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}
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