include/akgl/ui.h

@@ -425,8 +425,11 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_ui_label(char *id, char *text, akgl_UiAn
  * @brief Declare a vertical menu from caller-owned state, centred on screen.
  *
  * One row per entry, the selected row drawn inverted (ink on fill swaps to
- * fill on ink). Hovering a row with the mouse moves `selected` to it; a left
+ * fill on ink). Moving the mouse onto a row selects it; a left click on a
- * click on a row sets `activated`. Keyboard and gamepad go through
+ * row selects and sets `activated`. A *stationary* pointer claims nothing --
+ * parking the mouse over the menu must not pin the selection against the
+ * keyboard, which is fighting sixty times a second and losing. Keyboard and
+ * gamepad go through
  * akgl_ui_menu_handle_event(), which the application calls for whichever
  * menu currently has its attention -- that routing *is* the focus model.
  * Legal only between akgl_ui_frame_begin() and akgl_ui_frame_end().

src/ui.c

@@ -80,6 +80,18 @@ static bool ui_pointer_down;
 static bool ui_pointer_pending_pressed;
 /** @brief The frame-stable press edge: one left press happened before this frame. */
 static bool ui_pointer_pressed;
+/** @brief Motion arrived since the last frame_begin latched. Companion to the press edge. */
+static bool ui_pointer_pending_moved;
+/**
+ * @brief The frame-stable motion edge: the pointer moved before this frame.
+ *
+ * What keeps a menu's hover-selection polite. A stationary pointer parked
+ * over a row must not re-claim the selection every frame -- the keyboard
+ * would fight it and lose, sixty times a second -- so hover only moves the
+ * selection on frames the mouse actually moved. Found the way these things
+ * are found: the demo script pressed Up and the selection did not move.
+ */
+static bool ui_pointer_moved;
 /** @brief Wheel notches accumulated since the last frame_begin, horizontal. */
 static float ui_wheel_x;
 /** @brief Wheel notches accumulated since the last frame_begin, vertical. */
@@ -262,6 +274,8 @@ akerr_ErrorContext *akgl_ui_shutdown(void)
     ui_pointer_down = false;
     ui_pointer_pending_pressed = false;
     ui_pointer_pressed = false;
+    ui_pointer_pending_moved = false;
+    ui_pointer_moved = false;
     ui_wheel_x = 0.0f;
     ui_wheel_y = 0.0f;
     ui_last_frame_ns = 0;
@@ -679,6 +693,7 @@ akerr_ErrorContext *akgl_ui_handle_event(void *appstate, SDL_Event *event, bool
     case SDL_EVENT_MOUSE_MOTION:
 	ui_pointer_x = event->motion.x;
 	ui_pointer_y = event->motion.y;
+	ui_pointer_pending_moved = true;
 	position.x = ui_pointer_x;
 	position.y = ui_pointer_y;
 	// Fed per event, not per frame, which is the usage clay documents:
@@ -743,10 +758,12 @@ akerr_ErrorContext *akgl_ui_frame_begin(void)
     ui_clay_error_text[0] = '\0';
     ui_clay_error_count = 0;
 
-    // Latch the press edge for the widgets this frame declares, then let the
+    // Latch the press and motion edges for the widgets this frame declares,
-    // event loop start accumulating the next one.
+    // then let the event loop start accumulating the next ones.
     ui_pointer_pressed = ui_pointer_pending_pressed;
     ui_pointer_pending_pressed = false;
+    ui_pointer_moved = ui_pointer_pending_moved;
+    ui_pointer_pending_moved = false;
 
     now = SDL_GetTicksNS();
     if ( ui_last_frame_ns != 0 ) {
@@ -1015,11 +1032,14 @@ akerr_ErrorContext *akgl_ui_menu(akgl_UiMenu *menu)
 		    },
 		    .backgroundColor = rowfill
 		}) {
-		// Mouse selection: hovering a row makes it the selection, and
+		// Mouse selection: a row claims the selection when the
-		// the frame-latched press edge on a hovered row confirms it.
+		// pointer moves onto it or clicks it -- not merely by being
-		// The row highlight catches up next frame, which at any
+		// under a stationary pointer, which would re-claim it every
-		// playable frame rate is invisible.
+		// frame and the keyboard would fight it and lose. The
-		if ( Clay_Hovered() ) {
+		// frame-latched press edge on a hovered row confirms. The
+		// row highlight catches up next frame, which at any playable
+		// frame rate is invisible.
+		if ( Clay_Hovered() && (ui_pointer_moved || ui_pointer_pressed) ) {
 		    menu->selected = i;
 		    if ( ui_pointer_pressed ) {
 			menu->activated = true;

tests/ui.c

@@ -841,6 +841,23 @@ akerr_ErrorContext *test_ui_menu_widget(void)
 		    "clicking the second row moved the selection to %d, not 1", menu.selected);
 	TEST_ASSERT(e, menu.activated == true, "clicking a row did not activate the menu");
 	menu.activated = false;
+
+	// The pointer is still parked over the second row. Keyboard moves the
+	// selection away, and redeclaring the menu must not let the
+	// stationary pointer claim it back -- only motion or a click selects.
+	SDL_memset(&event, 0x00, sizeof(SDL_Event));
+	event.type = SDL_EVENT_KEY_DOWN;
+	event.key.key = SDLK_DOWN;
+	TEST_EXPECT_OK(e, akgl_ui_menu_handle_event(&menu, &event, &consumed),
+		       "Down after the click was refused");
+	TEST_ASSERT(e, menu.selected == 2, "Down did not move the selection off the hovered row");
+	TEST_EXPECT_OK(e, akgl_ui_frame_begin(), "opening the third menu frame failed");
+	TEST_EXPECT_OK(e, akgl_ui_menu(&menu), "redeclaring the menu a third time failed");
+	TEST_EXPECT_OK(e, akgl_ui_frame_end(akgl_renderer), "closing the third menu frame failed");
+	TEST_ASSERT(e, menu.selected == 2,
+		    "a stationary pointer stole the selection back to %d", menu.selected);
+	TEST_ASSERT(e, menu.activated == false,
+		    "a stationary pointer activated the menu");
     } CLEANUP {
 	if ( shot != NULL ) {
 	    SDL_DestroySurface(shot);