mirror of
https://github.com/flutter/flutter.git
synced 2026-02-20 02:29:02 +08:00
[floating_cursor_selection]add some comments on the tricky part (flutter/engine#42136)
Many parts of the floating cursor selection feature is pretty tricky. Some took me a while to figure out. So I added some comments to explain a bit for future readers. *List which issues are fixed by this PR. You must list at least one issue.* https://github.com/flutter/flutter/issues/30476 *If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].* [C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
This commit is contained in:
hellohuanlin
GitHub
parent
17085a8d3d
commit
ebe810b435
@ -424,21 +424,28 @@ static BOOL IsApproximatelyEqual(float x, float y, float delta) {
|
||||
return fabsf(x - y) <= delta;
|
||||
}
|
||||
|
||||
// This is a helper function for floating cursor selection logic to determine which text
|
||||
// position is closer to a point.
|
||||
// Checks whether point should be considered closer to selectionRect compared to
|
||||
// otherSelectionRect.
|
||||
//
|
||||
// Uses the leading-center point on selectionRect and otherSelectionRect to compare.
|
||||
// If `useTrailingBoundaryOfSelectionRect` is not set, it uses the leading-center point
|
||||
// on selectionRect and otherSelectionRect to compare.
|
||||
// For left-to-right text, this means the left-center point, and for right-to-left text,
|
||||
// this means the right-center point.
|
||||
//
|
||||
// If useTrailingBoundaryOfSelectionRect is set, the trailing-center point on selectionRect
|
||||
// will be used instead of the leading-center point.
|
||||
// will be used instead of the leading-center point, while leading-center point is still used
|
||||
// for otherSelectionRect.
|
||||
//
|
||||
// This uses special (empirically determined using a 1st gen iPad pro, 9.7" model running
|
||||
// iOS 14.7.1) logic for determining the closer rect, rather than a simple distance calculation.
|
||||
// First, the closer vertical distance is determined. Within the closest y distance, if the point is
|
||||
// above the bottom of the closest rect, the x distance will be minimized; however, if the point is
|
||||
// below the bottom of the rect, the x value will be maximized.
|
||||
// - First, the rect with closer y distance wins.
|
||||
// - Otherwise (same y distance):
|
||||
// - If the point is above bottom of the rect, the rect boundary with closer x distance wins.
|
||||
// - Otherwise (point is below bottom of the rect), the rect boundary with farthest x wins.
|
||||
// This is because when the point is below the bottom line of text, we want to select the
|
||||
// whole line of text, so we mark the farthest rect as closest.
|
||||
static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
CGRect selectionRect,
|
||||
BOOL selectionRectIsRTL,
|
||||
@ -446,6 +453,7 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
CGRect otherSelectionRect,
|
||||
BOOL otherSelectionRectIsRTL,
|
||||
CGFloat verticalPrecision) {
|
||||
// The point is inside the selectionRect's corresponding half-rect area.
|
||||
if (CGRectContainsPoint(
|
||||
CGRectMake(
|
||||
selectionRect.origin.x + ((useTrailingBoundaryOfSelectionRect ^ selectionRectIsRTL)
|
||||
@ -455,6 +463,7 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
point)) {
|
||||
return YES;
|
||||
}
|
||||
// pointForSelectionRect is either leading-center or trailing-center point of selectionRect.
|
||||
CGPoint pointForSelectionRect = CGPointMake(
|
||||
selectionRect.origin.x +
|
||||
(selectionRectIsRTL ^ useTrailingBoundaryOfSelectionRect ? selectionRect.size.width : 0),
|
||||
@ -462,6 +471,7 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
float yDist = fabs(pointForSelectionRect.y - point.y);
|
||||
float xDist = fabs(pointForSelectionRect.x - point.x);
|
||||
|
||||
// pointForOtherSelectionRect is the leading-center point of otherSelectionRect.
|
||||
CGPoint pointForOtherSelectionRect = CGPointMake(
|
||||
otherSelectionRect.origin.x + (otherSelectionRectIsRTL ? otherSelectionRect.size.width : 0),
|
||||
otherSelectionRect.origin.y + otherSelectionRect.size.height * 0.5);
|
||||
@ -476,6 +486,7 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
BOOL isAboveBottomOfLine = point.y <= selectionRect.origin.y + selectionRect.size.height;
|
||||
BOOL isCloserHorizontally = xDist < xDistOther;
|
||||
BOOL isBelowBottomOfLine = point.y > selectionRect.origin.y + selectionRect.size.height;
|
||||
// Is "farther away", or is closer to the end of the text line.
|
||||
BOOL isFarther;
|
||||
if (selectionRectIsRTL) {
|
||||
isFarther = selectionRect.origin.x < otherSelectionRect.origin.x;
|
||||
@ -1669,7 +1680,7 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
- (CGRect)caretRectForPosition:(UITextPosition*)position {
|
||||
NSInteger index = ((FlutterTextPosition*)position).index;
|
||||
UITextStorageDirection affinity = ((FlutterTextPosition*)position).affinity;
|
||||
// Get the bounds of the characters before and after the requested caret position.
|
||||
// Get the selectionRect of the characters before and after the requested caret position.
|
||||
NSArray<UITextSelectionRect*>* rects = [self
|
||||
selectionRectsForRange:[FlutterTextRange
|
||||
rangeWithNSRange:fml::RangeForCharactersInRange(
|
||||
@ -1696,6 +1707,7 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
characterAfterCaret.size.height);
|
||||
}
|
||||
} else if (rects.count == 2 && affinity == UITextStorageDirectionForward) {
|
||||
// There are characters before and after the caret, with forward direction affinity.
|
||||
// It's better to use the character after the caret.
|
||||
CGRect characterAfterCaret = rects[1].rect;
|
||||
// Return a zero-width rectangle along the upstream edge of the character after the caret
|
||||
@ -1708,9 +1720,13 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
characterAfterCaret.size.height);
|
||||
}
|
||||
}
|
||||
|
||||
// Covers 2 remaining cases:
|
||||
// 1. there are characters before and after the caret, with backward direction affinity.
|
||||
// 2. there is only 1 character before the caret (caret is at the end of text).
|
||||
// For both cases, return a zero-width rectangle along the downstream edge of the character
|
||||
// before the caret position.
|
||||
CGRect characterBeforeCaret = rects[0].rect;
|
||||
// Return a zero-width rectangle along the downstream edge of the character before the caret
|
||||
// position.
|
||||
if ([self isRTLAtPosition:index - 1]) {
|
||||
return CGRectMake(characterBeforeCaret.origin.x, characterBeforeCaret.origin.y, 0,
|
||||
characterBeforeCaret.size.height);
|
||||
@ -1787,6 +1803,7 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
// Allow further vertical deviation and base more of the decision on horizontal comparison.
|
||||
CGFloat verticalPrecision = _isFloatingCursorActive ? 10 : 1;
|
||||
|
||||
// Find the selectionRect with a leading-center point that is closest to a given point.
|
||||
BOOL isFirst = YES;
|
||||
NSUInteger _closestRectIndex = 0;
|
||||
for (NSUInteger i = 0; i < [_selectionRects count]; i++) {
|
||||
@ -1807,7 +1824,10 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
[FlutterTextPosition positionWithIndex:_selectionRects[_closestRectIndex].position
|
||||
affinity:UITextStorageDirectionForward];
|
||||
|
||||
// Check if the far side of the closest rect is a better fit (tapping end of line)
|
||||
// Check if the far side of the closest rect is a better fit (e.g. tapping end of line)
|
||||
// Cannot simply check the _closestRectIndex result from the previous for loop due to RTL
|
||||
// writing direction and the gaps between selectionRects. So we also need to consider
|
||||
// the adjacent selectionRects to refine _closestRectIndex.
|
||||
for (NSUInteger i = MAX(0, _closestRectIndex - 1);
|
||||
i < MIN(_closestRectIndex + 2, [_selectionRects count]); i++) {
|
||||
NSUInteger position = _selectionRects[i].position + 1;
|
||||
@ -1839,10 +1859,10 @@ static BOOL IsSelectionRectBoundaryCloserToPoint(CGPoint point,
|
||||
// width >= 0 ? point.x.clamp(boundingBox.left, boundingBox.right) : point.x,
|
||||
// height >= 0 ? point.y.clamp(boundingBox.top, boundingBox.bottom) : point.y,
|
||||
// )
|
||||
// where
|
||||
// point = keyboardPanGestureRecognizer.translationInView(textInputView) +
|
||||
// caretRectForPosition boundingBox = self.convertRect(bounds, fromView:textInputView)
|
||||
// bounds = self._selectionClipRect ?? self.bounds
|
||||
// where
|
||||
// point = keyboardPanGestureRecognizer.translationInView(textInputView) + caretRectForPosition
|
||||
// boundingBox = self.convertRect(bounds, fromView:textInputView)
|
||||
// bounds = self._selectionClipRect ?? self.bounds
|
||||
//
|
||||
// It seems impossible to use a negative "width" or "height", as the "convertRect"
|
||||
// call always turns a CGRect's negative dimensions into non-negative values, e.g.,
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user