Clamp text cursor positions in the same places where we used to (#7081)

Closes #7077.

This fixes the problem shown in #7077 where clearing a `TextEdit`
wouldn't reset its cursor position. I've fixed that by adding back the
`TextCursorState::range` method, which clamps the selection range to
that of the passed `Galley`, and calling it in the same places where it
was called before #5785.

(/cc @juancampa)

* [x] I have followed the instructions in the PR template

crates/egui/src/text_selection/label_text_selection.rs

@@ -530,7 +530,7 @@ impl LabelSelectionState {
 
         let mut cursor_state = self.cursor_for(ui, response, global_from_galley, galley);
 
-        let old_range = cursor_state.char_range();
+        let old_range = cursor_state.range(galley);
 
         if let Some(pointer_pos) = ui.ctx().pointer_interact_pos() {
             if response.contains_pointer() {
@@ -544,7 +544,7 @@ impl LabelSelectionState {
             }
         }
 
-        if let Some(mut cursor_range) = cursor_state.char_range() {
+        if let Some(mut cursor_range) = cursor_state.range(galley) {
             let galley_rect = global_from_galley * Rect::from_min_size(Pos2::ZERO, galley.size());
             self.selection_bbox_this_frame = self.selection_bbox_this_frame.union(galley_rect);
 
@@ -562,7 +562,7 @@ impl LabelSelectionState {
         }
 
         // Look for changes due to keyboard and/or mouse interaction:
-        let new_range = cursor_state.char_range();
+        let new_range = cursor_state.range(galley);
         let selection_changed = old_range != new_range;
 
         if let (true, Some(range)) = (selection_changed, new_range) {
@@ -632,7 +632,7 @@ impl LabelSelectionState {
             }
         }
 
-        let cursor_range = cursor_state.char_range();
+        let cursor_range = cursor_state.range(galley);
 
         let mut new_vertex_indices = vec![];
 

crates/egui/src/text_selection/text_cursor_state.rs

@@ -35,6 +35,16 @@ impl TextCursorState {
         self.ccursor_range
     }
 
+    /// The currently selected range of characters, clamped within the character
+    /// range of the given [`Galley`].
+    pub fn range(&self, galley: &Galley) -> Option<CCursorRange> {
+        self.ccursor_range.map(|mut range| {
+            range.primary = galley.clamp_cursor(&range.primary);
+            range.secondary = galley.clamp_cursor(&range.secondary);
+            range
+        })
+    }
+
     /// Sets the currently selected range of characters.
     pub fn set_char_range(&mut self, ccursor_range: Option<CCursorRange>) {
         self.ccursor_range = ccursor_range;
@@ -69,7 +79,7 @@ impl TextCursorState {
             if response.hovered() && ui.input(|i| i.pointer.any_pressed()) {
                 // The start of a drag (or a click).
                 if ui.input(|i| i.modifiers.shift) {
-                    if let Some(mut cursor_range) = self.char_range() {
+                    if let Some(mut cursor_range) = self.range(galley) {
                         cursor_range.primary = cursor_at_pointer;
                         self.set_char_range(Some(cursor_range));
                     } else {
@@ -81,7 +91,7 @@ impl TextCursorState {
                 true
             } else if is_being_dragged {
                 // Drag to select text:
-                if let Some(mut cursor_range) = self.char_range() {
+                if let Some(mut cursor_range) = self.range(galley) {
                     cursor_range.primary = cursor_at_pointer;
                     self.set_char_range(Some(cursor_range));
                 }

crates/egui/src/widgets/text_edit/builder.rs

@@ -617,7 +617,7 @@ impl TextEdit<'_> {
         }
 
         let mut cursor_range = None;
-        let prev_cursor_range = state.cursor.char_range();
+        let prev_cursor_range = state.cursor.range(&galley);
         if interactive && ui.memory(|mem| mem.has_focus(id)) {
             ui.memory_mut(|mem| mem.set_focus_lock_filter(id, event_filter));
 
@@ -720,7 +720,7 @@ impl TextEdit<'_> {
             let has_focus = ui.memory(|mem| mem.has_focus(id));
 
             if has_focus {
-                if let Some(cursor_range) = state.cursor.char_range() {
+                if let Some(cursor_range) = state.cursor.range(&galley) {
                     // Add text selection rectangles to the galley:
                     paint_text_selection(&mut galley, ui.visuals(), &cursor_range, None);
                 }
@@ -742,7 +742,7 @@ impl TextEdit<'_> {
             painter.galley(galley_pos, galley.clone(), text_color);
 
             if has_focus {
-                if let Some(cursor_range) = state.cursor.char_range() {
+                if let Some(cursor_range) = state.cursor.range(&galley) {
                     let primary_cursor_rect =
                         cursor_rect(&galley, &cursor_range.primary, row_height)
                             .translate(galley_pos.to_vec2());
@@ -898,7 +898,7 @@ fn events(
 ) -> (bool, CCursorRange) {
     let os = ui.ctx().os();
 
-    let mut cursor_range = state.cursor.char_range().unwrap_or(default_cursor_range);
+    let mut cursor_range = state.cursor.range(galley).unwrap_or(default_cursor_range);
 
     // We feed state to the undoer both before and after handling input
     // so that the undoer creates automatic saves even when there are no events for a while.

crates/epaint/src/text/text_layout_types.rs

@@ -1104,6 +1104,10 @@ impl Galley {
         }
     }
 
+    pub fn clamp_cursor(&self, cursor: &CCursor) -> CCursor {
+        self.cursor_from_layout(self.layout_from_cursor(*cursor))
+    }
+
     pub fn cursor_up_one_row(
         &self,
         cursor: &CCursor,