Manual doublebuffering. Hopefully fixes flickering.

main.c

@@ -12,7 +12,7 @@
 */
 
 // --------------
-// TextBar v0.1.1
+// TextBar v0.1.2
 // --------------
 // Usage: <text generator> | textbar | <input handler>
 //
@@ -23,9 +23,6 @@
 // Line buffered
 // Prints all mouse clicks to stdout
 // In the format of `X Y` (without the '`')
-// 
-// When the X server is lagging, the bar will set the background color to 0,0,0,0 for a single frame in a given frequency. The more X is lagging, the more frequently it will do so.
-// I swear this is an intented feature.
 
 #include <pthread.h>
 
@@ -48,7 +45,9 @@
 Display* dpy;
 Window win;
 cairo_surface_t* sfc;
+cairo_surface_t* sfc2;
 cairo_t* ctx;
+cairo_t* ctx2;
 char text[256] = {0};
 char text_other[256] = {0};
 int width;
@@ -74,8 +73,8 @@ void init() {
 	XMatchVisualInfo(dpy, screen, 32, TrueColor, &visualinfo);
 	XSetWindowAttributes attr;
 	attr.colormap = XCreateColormap(dpy, DefaultRootWindow(dpy), visualinfo.visual, AllocNone);
-  attr.background_pixel = 0;
-  attr.border_pixel = 0;
+	attr.background_pixel = 0;
+	attr.border_pixel = 0;
 	win = XCreateWindow(dpy, DefaultRootWindow(dpy),
 											0, 0, width, HEIGHT,
 											0, visualinfo.depth, InputOutput, visualinfo.visual, CWBackPixel | CWColormap | CWBorderPixel, &attr);
@@ -102,35 +101,46 @@ void init() {
 
 	XMapWindow(dpy, win);
 	sfc = cairo_xlib_surface_create(dpy, win, visualinfo.visual, DisplayWidth(dpy, screen), HEIGHT);
+	sfc2 = cairo_surface_create_similar(sfc, CAIRO_CONTENT_COLOR_ALPHA, DisplayWidth(dpy, screen), HEIGHT);
 	ctx = cairo_create(sfc);
+	ctx2 = cairo_create(sfc2);
 }
 
 pthread_mutex_t do_paint;
 void paint(Display* dpy) {
 	if(!pthread_mutex_lock(&do_paint)) {
-	//cairo_set_source_rgba(ctx, 0.0, 0.0, 0.0, 0.0);
-	//cairo_set_operator(ctx, CAIRO_OPERATOR_SOURCE);
-	//cairo_paint(ctx);
-	//TODO: fix alpha
-	//NOTE: comment the following line if you do not use transparency. 
-		XClearWindow(dpy, win);
-		cairo_push_group(ctx);
-		cairo_set_operator(ctx, CAIRO_OPERATOR_OVER);
-	  cairo_set_source_rgba(ctx, BG_COLOR);
-	  cairo_paint(ctx);
-		cairo_move_to(ctx, FONT_SIZE / 2, FONT_POS);
-		cairo_select_font_face(ctx, FONT, CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);
-		cairo_set_font_size(ctx, FONT_SIZE);
-		cairo_set_source_rgba(ctx, FG_COLOR);
-		cairo_show_text(ctx, text);
+		// Clear
+		cairo_set_source_rgba(ctx2, 0.0, 0.0, 0.0, 0.0);
+		cairo_set_operator(ctx2, CAIRO_OPERATOR_SOURCE);
+		cairo_paint(ctx2);
+		cairo_set_operator(ctx2, CAIRO_OPERATOR_OVER);
+
+		// Background
+		cairo_set_source_rgba(ctx2, BG_COLOR);
+		cairo_paint(ctx2);
+
+		// Left text
+		cairo_move_to(ctx2, FONT_SIZE / 2, FONT_POS);
+		cairo_select_font_face(ctx2, FONT, CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);
+		cairo_set_font_size(ctx2, FONT_SIZE);
+		cairo_set_source_rgba(ctx2, FG_COLOR);
+		cairo_show_text(ctx2, text);
+
+		// Right text
 		cairo_text_extents_t extents;
-		cairo_text_extents(ctx, text_other, &extents);
-		cairo_move_to(ctx, (width-extents.width) - FONT_SIZE / 2, FONT_POS);
-		cairo_show_text(ctx, text_other);
-		cairo_pop_group_to_source(ctx);
+		cairo_text_extents(ctx2, text_other, &extents);
+		cairo_move_to(ctx2, (width-extents.width) - FONT_SIZE / 2, FONT_POS);
+		cairo_show_text(ctx2, text_other);
+
+		// Backbuffer -> Frontbuffer
+		cairo_set_source_surface(ctx, sfc2, 0, 0);
+		cairo_set_operator(ctx, CAIRO_OPERATOR_SOURCE);
 		cairo_paint(ctx);
+
+		// Flushing
 		cairo_surface_flush(sfc);
 		XFlush(dpy);
+
 		pthread_mutex_unlock(&do_paint);
 	}
 }
@@ -156,8 +166,7 @@ void x_loop() {
 		if(e.type == ButtonPress) {
 			printf("%d %d\n", e.xbutton.x, e.xbutton.y);
 			fflush(stdout);
-		} else
-		if(e.type == ConfigureNotify) {
+		} else if(e.type == ConfigureNotify) {
 			cairo_xlib_surface_set_size(sfc, e.xconfigure.width, e.xconfigure.height);
 		} else
 		if(e.type == Expose) {