ubb-la/gui.c: Shift+Left/Right jumps "intelligently" to next change on any channel

ubb-la/README

@@ -82,7 +82,8 @@ command line. Example:
 
 In the GUI, the following keys are available:
 
-  Left/Right	Pan the waveform left/right
+  Left/Right	Pan the waveform left/right. With Shift, jump to the
+		next change on any channel in the specified direction.
   Up/Down	Zoom in/out
   Space		Set the user origin (upward-facing green triangle)
 		at the current position and display the time to

ubb-la/gui.c

@@ -485,13 +485,36 @@ static int pos_step(int zoom)
 }
 
 
+static int smart_pos(const uint8_t *buf, int skip, int nibbles,
+    int pos, int dir)
+{
+	uint8_t ref;
+
+	if (dir < 0) {
+		if (!pos)
+			return pos;
+		ref = get_sample(buf, skip+pos-1);
+	} else {
+		ref = get_sample(buf, skip+pos);
+	}
+	do {
+		pos += dir;
+		if (pos < 0 || pos == nibbles-skip)
+			return pos-dir;
+	} while (get_sample(buf, skip+pos) == ref);
+	if (dir < 0)
+		pos++;
+	return pos;
+}
+
+
 void gui(const uint8_t *buf, int skip, int nibbles, double freq)
 {
 	SDL_Event event;
 	int pos = (skip+nibbles) >> 1;
 	int zoom;	/* < 0: zoom out; 0: 1 pixel = 1 sample; > 1: zoom in */
 	int min_zoom = 0;
-	int i;
+	int i, shift;
 
 	while (XWIDTH < (nibbles-skip) >> -min_zoom)
 		min_zoom--;
@@ -515,6 +538,7 @@ void gui(const uint8_t *buf, int skip, int nibbles, double freq)
 			SDL_WaitEvent(&event);
 			switch (event.type) {
 			case SDL_KEYDOWN:
+				shift = event.key.keysym.mod & KMOD_SHIFT;
 				switch (event.key.keysym.sym) {
 				case SDLK_UP:
 					if (zoom < MAX_ZOOM)
@@ -525,14 +549,24 @@ void gui(const uint8_t *buf, int skip, int nibbles, double freq)
 						zoom--;
 					break;
 				case SDLK_LEFT:
+					if (shift) {
+						pos = smart_pos(buf,
+						    skip, nibbles, pos, -1);
+					} else {
 						pos -= pos_step(zoom);
 						if (pos < 0)
 							pos = 0;
+					}
 					break;
 				case SDLK_RIGHT:
+					if (shift) {
+						pos = smart_pos(buf,
+						    skip, nibbles, pos, 1);
+					} else {
 						pos += pos_step(zoom);
 						if (pos > nibbles-skip-1)
 							pos = nibbles-skip-1;
+					}
 					break;
 				case SDLK_SPACE:
 					if (pos == user_ref)
@@ -543,6 +577,9 @@ void gui(const uint8_t *buf, int skip, int nibbles, double freq)
 				case SDLK_RETURN:
 				case SDLK_q:
 					return;
+				case SDLK_LSHIFT:
+				case SDLK_RSHIFT:
+					continue;
 				default:
 					printf("%x\n", event.key.keysym.sym);
 					continue;