228 lines
6.1 KiB
C
228 lines
6.1 KiB
C
/**
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* Simple Evas example using the Buffer engine.
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*
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* You must have Evas compiled with the buffer engine, and have the
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* evas-software-buffer pkg-config files installed.
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*
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* @verbatim
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* gcc -o evas-buffer-simple evas-buffer-simple.c `pkg-config --libs --cflags evas evas-software-buffer`
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* @endverbatim
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*/
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#include <Evas.h>
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#include <Evas_Engine_Buffer.h>
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#include <stdio.h>
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#include <errno.h>
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#define WIDTH (320)
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#define HEIGHT (240)
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/*
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* create_canvas(), destroy_canvas() and draw_scene() are support functions.
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*
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* They are only required to use raw Evas, but for real world usage,
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* it is recommended to use ecore and its ecore-evas submodule, that
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* provide convenience canvas creators, integration with main loop and
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* automatic render of updates (draw_scene()) when system goes back to
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* main loop.
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*/
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static Evas *create_canvas(int width, int height);
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static void destroy_canvas(Evas *canvas);
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static void draw_scene(Evas *canvas);
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// support function to save scene as PPM image
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static void save_scene(Evas *canvas, const char *dest);
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int main(void)
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{
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Evas *canvas;
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Evas_Object *bg, *r1, *r2, *r3;
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evas_init();
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// create your canvas
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// NOTE: consider using ecore_evas_buffer_new() instead!
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canvas = create_canvas(WIDTH, HEIGHT);
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if (!canvas)
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return -1;
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bg = evas_object_rectangle_add(canvas);
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evas_object_color_set(bg, 255, 255, 255, 255); // white bg
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evas_object_move(bg, 0, 0); // at origin
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evas_object_resize(bg, WIDTH, HEIGHT); // covers full canvas
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evas_object_show(bg);
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puts("initial scene, with just background:");
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draw_scene(canvas);
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r1 = evas_object_rectangle_add(canvas);
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evas_object_color_set(r1, 255, 0, 0, 255); // 100% opaque red
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evas_object_move(r1, 10, 10);
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evas_object_resize(r1, 100, 100);
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evas_object_show(r1);
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// pay attention to transparency! Evas color values are pre-multiplied by
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// alpha, so 50% opaque green is:
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// non-premul: r=0, g=255, b=0 a=128 (50% alpha)
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// premul:
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// r_premul = r * a / 255 = 0 * 128 / 255 = 0
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// g_premul = g * a / 255 = 255 * 128 / 255 = 128
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// b_premul = b * a / 255 = 0 * 128 / 255 = 0
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//
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// this 50% green is over a red background, so it will show in the
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// final output as yellow (green + red = yellow)
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r2 = evas_object_rectangle_add(canvas);
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evas_object_color_set(r2, 0, 128, 0, 128); // 50% opaque green
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evas_object_move(r2, 10, 10);
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evas_object_resize(r2, 50, 50);
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evas_object_show(r2);
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r3 = evas_object_rectangle_add(canvas);
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evas_object_color_set(r3, 0, 128, 0, 255); // 100% opaque dark green
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evas_object_move(r3, 60, 60);
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evas_object_resize(r3, 50, 50);
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evas_object_show(r3);
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puts("final scene (note updates):");
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draw_scene(canvas);
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save_scene(canvas, "/tmp/evas-buffer-simple-render.ppm");
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// NOTE: use ecore_evas_buffer_new() and here ecore_evas_free()
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destroy_canvas(canvas);
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evas_shutdown();
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return 0;
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}
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static Evas *create_canvas(int width, int height)
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{
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Evas *canvas;
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Evas_Engine_Info_Buffer *einfo;
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int method;
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void *pixels;
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method = evas_render_method_lookup("buffer");
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if (method <= 0)
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{
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fputs("ERROR: evas was not compiled with 'buffer' engine!\n", stderr);
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return NULL;
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}
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canvas = evas_new();
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if (!canvas)
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{
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fputs("ERROR: could not instantiate new evas canvas.\n", stderr);
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return NULL;
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}
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evas_output_method_set(canvas, method);
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evas_output_size_set(canvas, width, height);
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evas_output_viewport_set(canvas, 0, 0, width, height);
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einfo = (Evas_Engine_Info_Buffer *)evas_engine_info_get(canvas);
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if (!einfo)
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{
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fputs("ERROR: could not get evas engine info!\n", stderr);
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evas_free(canvas);
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return NULL;
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}
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// ARGB32 is sizeof(int), that is 4 bytes, per pixel
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pixels = malloc(width * height * sizeof(int));
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if (!pixels)
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{
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fputs("ERROR: could not allocate canvas pixels!\n", stderr);
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evas_free(canvas);
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return NULL;
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}
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einfo->info.depth_type = EVAS_ENGINE_BUFFER_DEPTH_ARGB32;
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einfo->info.dest_buffer = pixels;
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einfo->info.dest_buffer_row_bytes = width * sizeof(int);
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einfo->info.use_color_key = 0;
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einfo->info.alpha_threshold = 0;
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einfo->info.func.new_update_region = NULL;
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einfo->info.func.free_update_region = NULL;
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evas_engine_info_set(canvas, (Evas_Engine_Info *)einfo);
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return canvas;
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}
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static void destroy_canvas(Evas *canvas)
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{
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Evas_Engine_Info_Buffer *einfo;
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einfo = (Evas_Engine_Info_Buffer *)evas_engine_info_get(canvas);
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if (!einfo)
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{
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fputs("ERROR: could not get evas engine info!\n", stderr);
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evas_free(canvas);
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return;
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}
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free(einfo->info.dest_buffer);
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evas_free(canvas);
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}
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static void draw_scene(Evas *canvas)
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{
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Eina_List *updates, *n;
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Eina_Rectangle *update;
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// render and get the updated rectangles:
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updates = evas_render_updates(canvas);
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// informative only here, just print the updated areas:
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EINA_LIST_FOREACH(updates, n, update)
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printf("UPDATED REGION: pos: %3d, %3d size: %3dx%3d\n",
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update->x, update->y, update->w, update->h);
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// free list of updates
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evas_render_updates_free(updates);
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}
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static void save_scene(Evas *canvas, const char *dest)
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{
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Evas_Engine_Info_Buffer *einfo;
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const unsigned int *pixels, *pixels_end;
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int width, height;
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FILE *f;
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einfo = (Evas_Engine_Info_Buffer *)evas_engine_info_get(canvas);
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if (!einfo)
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{
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fputs("ERROR: could not get evas engine info!\n", stderr);
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return;
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}
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evas_output_size_get(canvas, &width, &height);
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f = fopen(dest, "wb+");
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if (!f)
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{
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fprintf(stderr, "ERROR: could not open for writing '%s': %s\n",
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dest, strerror(errno));
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return;
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}
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pixels = einfo->info.dest_buffer;
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pixels_end = pixels + (width * height);
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// PPM P6 format is dead simple to write:
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fprintf(f, "P6\n%d %d\n255\n", width, height);
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for (; pixels < pixels_end; pixels++)
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{
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int r, g, b;
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r = ((*pixels) & 0xff0000) >> 16;
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g = ((*pixels) & 0x00ff00) >> 8;
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b = (*pixels) & 0x0000ff;
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fprintf(f, "%c%c%c", r, g, b);
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}
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fclose(f);
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printf("saved scene as '%s'\n", dest);
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}
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