Desktop keys: up/down + line modifier (#74425)

up/down arrows + cmd (optionally + shift) works on desktop to jump selection to beginning/end of field

packages/flutter/lib/src/rendering/editable.dart

@@ -712,6 +712,29 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     // case where the user moves the cursor to the end or beginning of the text
     // and then back up or down.
     if (downArrow || upArrow) {
+      if (lineModifier) {
+        if (upArrow) {
+          // Extend the selection to the beginning of the field.
+          final int upperOffset = math.max(0, math.max(
+            newSelection.baseOffset,
+            newSelection.extentOffset,
+          ));
+          newSelection = TextSelection(
+            baseOffset: shift ? upperOffset : 0,
+            extentOffset: 0,
+          );
+        } else {
+          // Extend the selection to the end of the field.
+          final int lowerOffset = math.max(0, math.min(
+            newSelection.baseOffset,
+            newSelection.extentOffset,
+          ));
+          newSelection = TextSelection(
+            baseOffset: shift ? lowerOffset : _plainText.length,
+            extentOffset: _plainText.length,
+          );
+        }
+      } else {
         // The caret offset gives a location in the upper left hand corner of
         // the caret so the middle of the line above is a half line above that
         // point and the line below is 1.5 lines below that point.
@@ -741,6 +764,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
           _cursorResetLocation = newSelection.extentOffset;
         }
       }
+    }
 
     // Just place the collapsed selection at the end or beginning of the region
     // if shift isn't down or selection isn't enabled.

packages/flutter/test/widgets/editable_text_test.dart

@@ -4167,6 +4167,144 @@ void main() {
       reason: 'on $platform',
     );
 
+    // Jump to end.
+    await sendKeys(
+      tester,
+      <LogicalKeyboardKey>[
+        LogicalKeyboardKey.arrowDown,
+      ],
+      shift: false,
+      lineModifier: true,
+      platform: platform,
+    );
+
+    expect(
+      selection,
+      equals(
+        const TextSelection.collapsed(
+          offset: testText.length,
+          affinity: TextAffinity.downstream,
+        ),
+      ),
+      reason: 'on $platform',
+    );
+    expect(controller.text, equals(testText), reason: 'on $platform');
+
+    // Jump to start.
+    await sendKeys(
+      tester,
+      <LogicalKeyboardKey>[
+        LogicalKeyboardKey.arrowUp,
+      ],
+      shift: false,
+      lineModifier: true,
+      platform: platform,
+    );
+
+    expect(
+      selection,
+      equals(
+        const TextSelection.collapsed(
+          offset: 0,
+          affinity: TextAffinity.downstream,
+        ),
+      ),
+      reason: 'on $platform',
+    );
+    expect(controller.text, equals(testText), reason: 'on $platform');
+
+    // Move forward a few letters
+    await sendKeys(
+      tester,
+      <LogicalKeyboardKey>[
+        LogicalKeyboardKey.arrowRight,
+        LogicalKeyboardKey.arrowRight,
+        LogicalKeyboardKey.arrowRight,
+      ],
+      shift: false,
+      lineModifier: false,
+      platform: platform,
+    );
+
+    expect(
+      selection,
+      equals(
+        const TextSelection.collapsed(
+          offset: 3,
+          affinity: TextAffinity.downstream,
+        ),
+      ),
+      reason: 'on $platform',
+    );
+
+    // Select to end.
+    await sendKeys(
+      tester,
+      <LogicalKeyboardKey>[
+        LogicalKeyboardKey.arrowDown,
+      ],
+      shift: true,
+      lineModifier: true,
+      platform: platform,
+    );
+
+    expect(
+      selection,
+      equals(
+        const TextSelection(
+          baseOffset: 3,
+          extentOffset: testText.length,
+          affinity: TextAffinity.downstream,
+        ),
+      ),
+      reason: 'on $platform',
+    );
+
+    // Select to start, which extends the selection.
+    await sendKeys(
+      tester,
+      <LogicalKeyboardKey>[
+        LogicalKeyboardKey.arrowUp,
+      ],
+      shift: true,
+      lineModifier: true,
+      platform: platform,
+    );
+
+    expect(
+      selection,
+      equals(
+        const TextSelection(
+          baseOffset: testText.length,
+          extentOffset: 0,
+          affinity: TextAffinity.downstream,
+        ),
+      ),
+      reason: 'on $platform',
+    );
+
+    // Move to start again.
+    await sendKeys(
+      tester,
+      <LogicalKeyboardKey>[
+        LogicalKeyboardKey.arrowUp,
+      ],
+      shift: false,
+      lineModifier: false,
+      platform: platform,
+    );
+
+    expect(
+      selection,
+      equals(
+        const TextSelection.collapsed(
+          offset: 0,
+          affinity: TextAffinity.downstream,
+        ),
+      ),
+      reason: 'on $platform',
+    );
+
     // Jump forward three words.
     await sendKeys(
       tester,