mirror of https://github.com/encounter/SDL.git
140 lines
4.2 KiB
C
140 lines
4.2 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 = SDL_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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float x;
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float y;
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int i;
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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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x = startx - BRUSH_SIZE / 2.0f;
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y = starty - BRUSH_SIZE / 2.0f;
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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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SDL_Texture *target;
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int done; /* does user want to quit? */
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int w, h;
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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, 320, 480, SDL_WINDOW_BORDERLESS | SDL_WINDOW_ALLOW_HIGHDPI);
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renderer = SDL_CreateRenderer(window, 0, 0);
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SDL_GetWindowSize(window, &w, &h);
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SDL_RenderSetLogicalSize(renderer, w, h);
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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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target = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_TARGET, w, h);
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SDL_SetRenderTarget(renderer, target);
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SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
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SDL_RenderClear(renderer);
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SDL_SetRenderTarget(renderer, NULL);
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done = 0;
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while (!done) {
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while (SDL_PollEvent(&event) == 1) {
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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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SDL_SetRenderTarget(renderer, target);
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drawLine(renderer, x - dx, y - dy, dx, dy); /* draw line segment */
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SDL_SetRenderTarget(renderer, NULL);
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}
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break;
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}
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}
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SDL_RenderCopy(renderer, target, NULL, NULL);
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SDL_RenderPresent(renderer);
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}
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/* cleanup */
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SDL_DestroyTexture(brush);
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SDL_DestroyTexture(target);
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SDL_Quit();
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return 0;
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}
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