Initial commit

.gitignore

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+fb.so

Makefile

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+TARGET=fb.so
+PREFIX=/usr/local
+SRCS=fb.c
+HEADERS=fb.h
+FLAGS=-shared
+
+${TARGET}: ${SRCS} 
+	gcc ${FLAGS} ${SRCS} -o ${TARGET}
+
+install: ${TARGET}
+	mkdir -p ${PREFIX}/lib ${PREFIX}/include
+	cp ${TARGET} ${PREFIX}/lib/lib${TARGET} 
+	cp ${HEADERS} ${PREFIX}/include/
+
+clean:
+	rm ${TARGET}

README.md

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+# libfb
+
+Small library for interfacing with the Linux framebuffer. 
+
+Compile and install:
+```sh
+make
+sudo make install
+```
+
+Usage example:
+
+```c
+#define FB_IMPLEMENTATION // If linking dynamically with the library, omit this line
+#include <fb.h>
+
+int main() {
+    Framebuffer fb = newFramebuffer("/dev/fb0");
+    writeColourToFramebuffer(&fb, (Pixel){100, 100}, (Colour){255, 0, 0, 0});
+    destroyFramebuffer(&fb);
+}
+```
+
+Notes:
+
+* Don't try to write to the framebuffer while in an X.org or Wayland session
+* Your user must be in the `input` group before using, run the command `sudo usermod -a -G video $USER` to get permissions. Otherwise, the library will abort.
+* This is intended to be a small library to make it easier for anyone to draw things to the screen. Just pixel rendering.

example.c

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+#define FB_IMPLEMENTATION
+#include <fb.h>
+
+int main() {
+    Framebuffer fb = newFramebuffer("/dev/fb0");
+    writeColourToFramebuffer(&fb, (Pixel){100, 100}, (Colour){255, 0, 0, 0});
+    destroyFramebuffer(&fb);
+}

fb.c

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+#include "fb.h"
+
+#include <linux/fb.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <assert.h>
+
+Framebuffer newFramebuffer(const char* device) {
+	Framebuffer fb;
+	
+	// Open the framebuffer file descriptor
+	fb.fd = open(device, O_RDWR);
+	assert(fb.fd >= 0 && "Invalid framebuffer device, please ensure your user is in the 'video' group.");
+
+	// Get information about framebuffer
+	ioctl(fb.fd, FBIOGET_VSCREENINFO, &fb.vinfo);
+
+	// Get size of screen for writing pixels in bounds
+	fb.screensize = fb.vinfo.xres * fb.vinfo.yres * fb.vinfo.bits_per_pixel / 8;
+
+	fb.data = mmap(0, fb.screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fb.fd, 0);
+
+	return fb;
+} 
+
+void writeColourToFramebuffer(Framebuffer* fb, Pixel pixel, Colour colour) {
+	int offset = (pixel.y * fb->vinfo.xres + pixel.x) * (fb->vinfo.bits_per_pixel / 8);
+
+	fb->data[offset + 0] = colour.red;
+	fb->data[offset + 1] = colour.green;
+	fb->data[offset + 2] = colour.blue;
+	fb->data[offset + 3] = colour.alpha;
+
+	
+	munmap(fb->data, fb->screensize);
+}
+
+void destroyFramebuffer(Framebuffer* fb) {
+	close(fb->fd);
+
+	// NOTE: Do not free fb->data, this is not memory owned by us.
+	// Will cause a segfault
+}

fb.h

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