105 lines
2.6 KiB
C
105 lines
2.6 KiB
C
#include <linux/fb.h>
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// Represents a colour on the screen.
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// For each RGB value, accepts a value between 0-255, where
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// 0 is all the way off and 255 is all the way on.
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typedef struct Colour {
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char red;
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char green;
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char blue;
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char alpha;
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} Colour;
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// Represents a pixel on the screen.
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typedef struct Pixel {
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int x;
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int y;
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} Pixel;
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// Represents the framebuffer that the user has opened.
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// Use newFramebuffer() to construct this struct.
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// Get x and y size of screen with .vinfo.xres and .vinfo.yres
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typedef struct Framebuffer {
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int fd;
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struct fb_var_screeninfo vinfo;
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long int screensize;
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char* data;
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} Framebuffer;
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// Constructs a Framebuffer struct.
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// Asserts whether device is able to be opened. If unable, program is aborted.
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Framebuffer newFramebuffer(const char* device);
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// Writes a colour to the screen.
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// fb: Pointer to Framebuffer struct (get one with newFramebuffer("/dev/fb0") )
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// pixel: Which pixel on the screen to apply to
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// colour: The colour of the pixel
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void writeColourToFramebuffer(Framebuffer* fb, Pixel pixel, Colour colour);
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// Destroys a framebuffer.
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void destroyFramebuffer(Framebuffer* fb);
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// Example library usage (puts a red pixel at 100, 100)
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/*
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int main() {
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Framebuffer fb = newFramebuffer("/dev/fb0");
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writeColourToFramebuffer(&fb, (Pixel){100, 100}, (Colour){0, 0, 255, 0});
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destroyFramebuffer(&fb);
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return 0;
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}
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*/
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// To use as single-header library, define FB_IMPLEMENTATION before including this header.
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#ifdef FB_IMPLEMENTATION
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#include <linux/fb.h>
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#include <sys/mman.h>
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#include <sys/ioctl.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <assert.h>
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Framebuffer newFramebuffer(const char* device) {
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Framebuffer fb;
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// Open the framebuffer file descriptor
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fb.fd = open(device, O_RDWR);
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assert(fb.fd >= 0 && "Invalid framebuffer device, please ensure your user is in the 'video' group.");
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// Get information about framebuffer
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ioctl(fb.fd, FBIOGET_VSCREENINFO, &fb.vinfo);
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// Get size of screen for writing pixels in bounds
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fb.screensize = fb.vinfo.xres * fb.vinfo.yres * fb.vinfo.bits_per_pixel / 8;
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fb.data = mmap(0, fb.screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fb.fd, 0);
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return fb;
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}
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void writeColourToFramebuffer(Framebuffer* fb, Pixel pixel, Colour colour) {
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int offset = (pixel.y * fb->vinfo.xres + pixel.x) * (fb->vinfo.bits_per_pixel / 8);
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fb->data[offset + 0] = colour.red;
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fb->data[offset + 1] = colour.green;
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fb->data[offset + 2] = colour.blue;
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fb->data[offset + 3] = colour.alpha;
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munmap(fb->data, fb->screensize);
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}
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void destroyFramebuffer(Framebuffer* fb) {
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close(fb->fd);
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// NOTE: Do not free fb->data, this is not memory owned by us.
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// Will cause a segfault
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}
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#endif
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