diff --git a/desktop/browser.c b/desktop/browser.c
index 55e3f793e..dfa05b367 100644
--- a/desktop/browser.c
+++ b/desktop/browser.c
@@ -1976,10 +1976,12 @@ const char *browser_window_scrollbar_click(struct browser_window *bw,
 		browser_mouse_state mouse, struct box *box,
 		int box_x, int box_y, int x, int y)
 {
-	const browser_mouse_state but1 = (BROWSER_MOUSE_CLICK_1 |
-			BROWSER_MOUSE_DRAG_1 | BROWSER_MOUSE_HOLDING_1);
-	const browser_mouse_state but2 = (BROWSER_MOUSE_CLICK_2 |
-			BROWSER_MOUSE_DRAG_2 | BROWSER_MOUSE_HOLDING_2);
+	bool but1 = (mouse & (BROWSER_MOUSE_PRESS_1 | BROWSER_MOUSE_DRAG_1)) ||
+			((mouse & BROWSER_MOUSE_HOLDING_1) &&
+			 (mouse & BROWSER_MOUSE_DRAG_ON));
+	bool but2 = (mouse & (BROWSER_MOUSE_PRESS_2 | BROWSER_MOUSE_DRAG_2)) ||
+			((mouse & BROWSER_MOUSE_HOLDING_2) &&
+			 (mouse & BROWSER_MOUSE_DRAG_ON));;
 	const int w = SCROLLBAR_WIDTH;
 	bool vscroll, hscroll;
 	int well_height, bar_top, bar_height;
@@ -2027,27 +2029,30 @@ const char *browser_window_scrollbar_click(struct browser_window *bw,
 
 	/* find icon in scrollbar and calculate scroll */
 	if (z < w) {
+		/* on scrollbar bump arrow button */
 		status = messages_get(vert ? "ScrollUp" : "ScrollLeft");
-		if (mouse & but2)
-			scroll += 16;
-		else if (mouse & but1)
+		if (but1)
 			scroll -= 16;
+		else if (but2)
+			scroll += 16;
 	} else if (z < w + bar_start + w / 4) {
+		/* in scrollbar well */
 		status = messages_get(vert ? "ScrollPUp" : "ScrollPLeft");
-		if (mouse & BROWSER_MOUSE_CLICK_1)
+		if (but1)
 			scroll -= page;
-		else if (mouse & BROWSER_MOUSE_CLICK_2)
+		else if (but2)
 			scroll += page;
 	} else if (z < w + bar_start + bar_size - w / 4) {
+		/* in scrollbar */
 		status = messages_get(vert ? "ScrollV" : "ScrollH");
 
 		/* respond on the click rather than the drag because it gives
 		   the scrollbars a more solid, RISC OS feel */
-		if (mouse & (BROWSER_MOUSE_CLICK_1 | BROWSER_MOUSE_CLICK_2)) {
+		if (mouse & (BROWSER_MOUSE_PRESS_1 | BROWSER_MOUSE_PRESS_2)) {
 			int x0 = 0, x1 = 0;
 			int y0 = 0, y1 = 0;
 
-			if (mouse & BROWSER_MOUSE_CLICK_1) {
+			if (mouse & BROWSER_MOUSE_PRESS_1) {
 				bw->drag_type = vert ? DRAGGING_VSCROLL :
 						DRAGGING_HSCROLL;
 			} else
@@ -2067,17 +2072,19 @@ const char *browser_window_scrollbar_click(struct browser_window *bw,
 				gui_window_hide_pointer(bw->window);
 		}
 	} else if (z < w + well_size) {
+		/* in scrollbar well */
 		status = messages_get(vert ? "ScrollPDown" : "ScrollPRight");
-		if (mouse & BROWSER_MOUSE_CLICK_1)
+		if (but1)
 			scroll += page;
-		else if (mouse & BROWSER_MOUSE_CLICK_2)
+		else if (but2)
 			scroll -= page;
 	} else {
+		/* on scrollbar bump arrow button */
 		status = messages_get(vert ? "ScrollDown" : "ScrollRight");
-		if (mouse & but2)
-			scroll -= 16;
-		else if (mouse & but1)
+		if (but1)
 			scroll += 16;
+		else if (but2)
+			scroll -= 16;
 	}
 
 	/* update box and redraw */
diff --git a/desktop/browser.h b/desktop/browser.h
index bdada0c73..45a930c6a 100644
--- a/desktop/browser.h
+++ b/desktop/browser.h
@@ -174,18 +174,38 @@ struct browser_window {
 };
 
 
+/* Mouse state.	1 is    primary mouse button (e.g. Select on RISC OS).
+ *		2 is  secondary mouse button (e.g. Adjust on RISC OS). */
 typedef enum {
-	BROWSER_MOUSE_CLICK_1  = 1,  /* primary mouse button down (eg. Select) */
-	BROWSER_MOUSE_CLICK_2  = 2,
+	BROWSER_MOUSE_PRESS_1   = 1,	/* button 1 pressed */
+	BROWSER_MOUSE_PRESS_2   = 2,	/* button 2 pressed */
 
-	BROWSER_MOUSE_DRAG_1   = 8,  /* start of drag operation */
-	BROWSER_MOUSE_DRAG_2   = 16,
+					/* note: click meaning is different for
+					 * different front ends. On RISC OS, it
+					 * is standard to act on press, so a
+					 * click is fired at the same time as a
+					 * mouse button is pressed. With GTK, it
+					 * is standard to act on release, so a
+					 * click is fired when the mouse button
+					 * is released, if the operation wasn't
+					 * a drag. */
+	BROWSER_MOUSE_CLICK_1   = 4,	/* button 1 clicked. */
+	BROWSER_MOUSE_CLICK_2   = 8,	/* button 2 clicked. */
 
-	BROWSER_MOUSE_HOLDING_1 = 64,   /* whilst drag is in progress */
-	BROWSER_MOUSE_HOLDING_2 = 128,
+	BROWSER_MOUSE_DRAG_1    = 16,	/* start of button 1 drag operation */
+	BROWSER_MOUSE_DRAG_2    = 32,	/* start of button 2 drag operation */
 
-	BROWSER_MOUSE_MOD_1    = 512,  /* primary modifier key pressed (eg. Shift) */
-	BROWSER_MOUSE_MOD_2    = 1024
+	BROWSER_MOUSE_DRAG_ON   = 64,	/* a drag operation was started and
+					 * a mouse button is still pressed */
+
+	BROWSER_MOUSE_HOLDING_1 = 128,	/* while button 1 drag is in progress */
+	BROWSER_MOUSE_HOLDING_2 = 256,	/* while button 2 drag is in progress */
+
+
+	BROWSER_MOUSE_MOD_1     = 512,	/* primary modifier key pressed
+					 * (eg. Shift) */
+	BROWSER_MOUSE_MOD_2     = 1024	/* secondary modifier key pressed
+					 * (eg. Ctrl) */
 } browser_mouse_state;
 
 
diff --git a/riscos/gui.c b/riscos/gui.c
index 018cd0d93..7f78286d3 100644
--- a/riscos/gui.c
+++ b/riscos/gui.c
@@ -896,7 +896,8 @@ void gui_poll(bool active)
 {
 	wimp_event_no event;
 	wimp_block block;
-	const wimp_poll_flags mask = wimp_MASK_LOSE | wimp_MASK_GAIN | wimp_SAVE_FP;
+	const wimp_poll_flags mask = wimp_MASK_LOSE | wimp_MASK_GAIN |
+			wimp_SAVE_FP;
 
 	/* Poll wimp. */
 	xhourglass_off();
@@ -1019,7 +1020,8 @@ void gui_multitask(void)
 		return;
 
 	xhourglass_off();
-	event = wimp_poll(wimp_MASK_LOSE | wimp_MASK_GAIN | wimp_SAVE_FP, &block, 0);
+	event = wimp_poll(wimp_MASK_LOSE | wimp_MASK_GAIN | wimp_SAVE_FP,
+			&block, 0);
 	xhourglass_on();
 	gui_last_poll = clock();
 
@@ -1071,7 +1073,8 @@ void ro_gui_null_reason_code(void)
 			if (gui_track_wimp_w == dialog_url_complete)
 				ro_gui_url_complete_mouse_at(&pointer);
 			else if (gui_track_gui_window)
-				ro_gui_window_mouse_at(gui_track_gui_window, &pointer);
+				ro_gui_window_mouse_at(gui_track_gui_window,
+						&pointer);
 			break;
 	}
 }
diff --git a/riscos/gui.h b/riscos/gui.h
index 1c6bd41cc..21df85bbf 100644
--- a/riscos/gui.h
+++ b/riscos/gui.h
@@ -153,8 +153,10 @@ void ro_gui_throb(void);
 struct gui_window *ro_gui_window_lookup(wimp_w window);
 struct gui_window *ro_gui_toolbar_lookup(wimp_w window);
 void ro_gui_scroll_request(wimp_scroll *scroll);
-bool ro_gui_window_to_window_pos(struct gui_window *g, int x, int y, os_coord *pos);
-bool ro_gui_window_to_screen_pos(struct gui_window *g, int x, int y, os_coord *pos);
+bool ro_gui_window_to_window_pos(struct gui_window *g, int x, int y,
+		os_coord *pos);
+bool ro_gui_window_to_screen_pos(struct gui_window *g, int x, int y,
+		os_coord *pos);
 bool ro_gui_window_dataload(struct gui_window *g, wimp_message *message);
 bool ro_gui_toolbar_dataload(struct gui_window *g, wimp_message *message);
 void ro_gui_window_process_reformats(void);
diff --git a/riscos/window.c b/riscos/window.c
index 0ae8aa077..86d51edd3 100644
--- a/riscos/window.c
+++ b/riscos/window.c
@@ -84,6 +84,9 @@
 static bool iconise_used[64];
 static int iconise_next = 0;
 
+/** Whether a pressed mouse button has become a drag */
+static bool mouse_drag;
+
 /** List of all browser windows. */
 static struct gui_window *window_list = 0;
 /** GUI window which is being redrawn. Valid only during redraw. */
@@ -140,8 +143,8 @@ static void ro_gui_window_launch_url(struct gui_window *g, const char *url);
 static void ro_gui_window_clone_options(struct browser_window *new_bw,
 		struct browser_window *old_bw);
 static browser_mouse_state ro_gui_mouse_drag_state(wimp_mouse_state buttons);
-static bool ro_gui_window_import_text(struct gui_window *g, const char *filename,
-		bool toolbar);
+static bool ro_gui_window_import_text(struct gui_window *g,
+		const char *filename, bool toolbar);
 
 struct update_box {
 	int x0;
@@ -3003,11 +3006,19 @@ browser_mouse_state ro_gui_mouse_click_state(wimp_mouse_state buttons)
 {
 	browser_mouse_state state = 0;
 
-	if (buttons & (wimp_CLICK_SELECT)) state |= BROWSER_MOUSE_CLICK_1;
-	if (buttons & (wimp_CLICK_ADJUST)) state |= BROWSER_MOUSE_CLICK_2;
+	if (buttons & (wimp_CLICK_SELECT))
+		state |= BROWSER_MOUSE_PRESS_1 | BROWSER_MOUSE_CLICK_1;
+	if (buttons & (wimp_CLICK_ADJUST))
+		state |= BROWSER_MOUSE_PRESS_2 | BROWSER_MOUSE_CLICK_2;
 
-	if (buttons & (wimp_DRAG_SELECT)) state |= BROWSER_MOUSE_DRAG_1;
-	if (buttons & (wimp_DRAG_ADJUST)) state |= BROWSER_MOUSE_DRAG_2;
+	if (buttons & (wimp_DRAG_SELECT)) {
+		state |= BROWSER_MOUSE_DRAG_1;
+		mouse_drag = true;
+	}
+	if (buttons & (wimp_DRAG_ADJUST)) {
+		state |= BROWSER_MOUSE_DRAG_2;
+		mouse_drag = true;
+	}
 
 	if (ro_gui_shift_pressed()) state |= BROWSER_MOUSE_MOD_1;
 	if (ro_gui_ctrl_pressed())  state |= BROWSER_MOUSE_MOD_2;
@@ -3025,9 +3036,14 @@ browser_mouse_state ro_gui_mouse_drag_state(wimp_mouse_state buttons)
 {
 	browser_mouse_state state = 0;
 
+
 	if (buttons & (wimp_CLICK_SELECT)) state |= BROWSER_MOUSE_HOLDING_1;
 	if (buttons & (wimp_CLICK_ADJUST)) state |= BROWSER_MOUSE_HOLDING_2;
 
+	if (!(buttons & (wimp_CLICK_SELECT) || buttons & (wimp_CLICK_ADJUST)))
+		mouse_drag = false;
+	if (mouse_drag) state |= BROWSER_MOUSE_DRAG_ON;
+
 	if (ro_gui_shift_pressed()) state |= BROWSER_MOUSE_MOD_1;
 	if (ro_gui_ctrl_pressed())  state |= BROWSER_MOUSE_MOD_2;