SDL

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/*
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  Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
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  This software is provided 'as-is', without any express or implied
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  warranty.  In no event will the authors be held liable for any damages
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  arising from the use of this software.
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  Permission is granted to anyone to use this software for any purpose,
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  including commercial applications, and to alter it and redistribute it
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  freely.
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*/
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#include <SDL3/SDL.h>
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#include <SDL3/SDL_main.h>
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#include "glass.h"
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static SDL_HitTestResult SDLCALL ShapeHitTest(SDL_Window *window, const SDL_Point *area, void *userdata)
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{
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    SDL_Surface *shape = (SDL_Surface *)userdata;
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    Uint8 r, g, b, a;
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    if (SDL_ReadSurfacePixel(shape, area->x, area->y, &r, &g, &b, &a) == 0) {
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        if (a != SDL_ALPHA_TRANSPARENT) {
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            /* We'll just make everything draggable */
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            return SDL_HITTEST_DRAGGABLE;
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        }
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    }
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    return SDL_HITTEST_NORMAL;
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}
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int main(int argc, char *argv[])
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{
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    const char *image_file = NULL;
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    SDL_Window *window = NULL;
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    SDL_Renderer *renderer = NULL;
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    SDL_Surface *shape = NULL;
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    SDL_bool resizable = SDL_FALSE;
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    SDL_WindowFlags flags;
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    SDL_bool done = SDL_FALSE;
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    SDL_Event event;
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    int i;
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    int return_code = 1;
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    for (i = 1; i < argc; ++i) {
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        if (SDL_strcmp(argv[i], "--resizable") == 0) {
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            resizable = SDL_TRUE;
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        } else if (!image_file) {
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            image_file = argv[i];
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        } else {
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            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Usage: %s [--resizable] [shape.bmp]\n", argv[0]);
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            goto quit;
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        }
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    }
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    if (image_file) {
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        shape = SDL_LoadBMP(image_file);
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        if (!shape) {
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            SDL_Log("Couldn't load %s: %s\n", image_file, SDL_GetError());
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            goto quit;
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        }
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    } else {
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        shape = SDL_LoadBMP_IO(SDL_IOFromConstMem(glass_bmp, sizeof(glass_bmp)), SDL_TRUE);
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        if (!shape) {
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            SDL_Log("Couldn't load glass.bmp: %s\n", SDL_GetError());
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            goto quit;
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        }
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    }
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    /* Create the window hidden so we can set the shape before it's visible */
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    flags = (SDL_WINDOW_HIDDEN | SDL_WINDOW_TRANSPARENT);
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    if (resizable) {
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        flags |= SDL_WINDOW_RESIZABLE;
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    } else {
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        flags |= SDL_WINDOW_BORDERLESS;
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    }
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    window = SDL_CreateWindow("SDL Shape Test", shape->w, shape->h, flags);
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    if (!window) {
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        SDL_Log("Couldn't create transparent window: %s\n", SDL_GetError());
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        goto quit;
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    }
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    renderer = SDL_CreateRenderer(window, NULL);
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    if (!renderer) {
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        SDL_Log("Couldn't create renderer: %s\n", SDL_GetError());
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        goto quit;
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    }
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    if (!SDL_ISPIXELFORMAT_ALPHA(shape->format)) {
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        /* Set the colorkey to the top-left pixel */
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        Uint8 r, g, b, a;
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        SDL_ReadSurfacePixel(shape, 0, 0, &r, &g, &b, &a);
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        SDL_SetSurfaceColorKey(shape, 1, SDL_MapSurfaceRGBA(shape, r, g, b, a));
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    }
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    if (!resizable) {
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        /* Set the hit test callback so we can drag the window */
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        if (SDL_SetWindowHitTest(window, ShapeHitTest, shape) < 0) {
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            SDL_Log("Couldn't set hit test callback: %s\n", SDL_GetError());
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            goto quit;
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        }
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    }
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    /* Set the window size to the size of our shape and show it */
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    SDL_SetWindowShape(window, shape);
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    SDL_ShowWindow(window);
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    /* We're ready to go! */
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    while (!done) {
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        while (SDL_PollEvent(&event)) {
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            switch (event.type) {
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            case SDL_EVENT_KEY_DOWN:
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                if (event.key.key == SDLK_ESCAPE) {
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                    done = SDL_TRUE;
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                }
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                break;
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            case SDL_EVENT_QUIT:
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                done = SDL_TRUE;
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                break;
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            default:
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                break;
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            }
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        }
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        /* We'll clear to white, but you could do other drawing here */
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        SDL_SetRenderDrawColor(renderer, 255, 255, 255, SDL_ALPHA_OPAQUE);
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        SDL_RenderClear(renderer);
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        /* Show everything on the screen and wait a bit */
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        SDL_RenderPresent(renderer);
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        SDL_Delay(100);
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    }
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    /* Success! */
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    return_code = 0;
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quit:
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    SDL_DestroySurface(shape);
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    SDL_Quit();
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    return return_code;
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}
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