关于SCICursorModifier的技术咨询：长按激活与多表面共享

Great questions about SCICursorModifier! Let's break down each issue and walk through actionable solutions for both.

By default, SCICursorModifier uses a pan gesture to trigger and update the cursor position, but you can absolutely replace this with a long press gesture. Here's how to do it:

First, create your cursor modifier and a custom long press gesture recognizer, then swap out the default gesture handler. You'll also need to manually handle the gesture states to show/hide/update the cursor:

// Initialize your cursor modifier (use your custom MHSCICursorModifier if needed)
SCICursorModifier *cursorModifier = [[MHSCICursorModifier alloc] init];

// Create a long press gesture recognizer
UILongPressGestureRecognizer *longPressGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPressForCursor:)];
longPressGesture.minimumPressDuration = 0.3; // Adjust this to your preferred press length

// Replace the default pan gesture with your long press
cursorModifier.gestureRecognizer = longPressGesture;

// Add the modifier to your chart surface
[yourSurface.chartModifiers addModifier:cursorModifier];

Then implement the gesture handler to manage cursor visibility and position:

- (void)handleLongPressForCursor:(UILongPressGestureRecognizer *)gesture {
    // Get the target surface and cursor modifier
    SCIChartSurface *surface = (SCIChartSurface *)gesture.view;
    SCICursorModifier *cursorModifier = nil;
    for (id<ISCIChartModifier> modifier in surface.chartModifiers) {
        if ([modifier isKindOfClass:[MHSCICursorModifier class]]) {
            cursorModifier = (MHSCICursorModifier *)modifier;
            break;
        }
    }
    if (!cursorModifier) return;

    CGPoint touchLocation = [gesture locationInView:surface];
    switch (gesture.state) {
        case UIGestureRecognizerStateBegan:
        case UIGestureRecognizerStateChanged:
            // Show and update the cursor position
            [cursorModifier showCursorAt:touchLocation];
            // If sharing across surfaces, sync position here (see next section)
            break;
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled:
            // Hide the cursor when gesture ends
            [cursorModifier hideCursor];
            break;
        default:
            break;
    }
}

This setup will trigger the cursor only after the long press is detected, and update its position as the user drags after pressing down.

Your approach with SCIMultiSurfaceModifier is on the right track, but the implementation has a small issue. Here's how to correctly set up shared cursor behavior across multiple surfaces:

The key is to wrap your base cursor modifier in a SCIMultiSurfaceModifier, then add this multi-surface modifier to every surface you want to share the cursor with. Also, ensure you're setting the shared modifier instance correctly:

// Create a single instance of your cursor modifier
MHSCICursorModifier *sharedCursor = [[MHSCICursorModifier alloc] init];

// Wrap it in SCIMultiSurfaceModifier
SCIMultiSurfaceModifier *multiSurfaceCursor = [[SCIMultiSurfaceModifier alloc] initWithModifierType:[MHSCICursorModifier class]];
[multiSurfaceCursor setSharedModifier:sharedCursor];

// Add the multi-surface modifier to ALL target surfaces
for (SCIChartSurface *surface in yourArrayOfSurfaces) {
    [surface.chartModifiers addModifier:multiSurfaceCursor];
}

Why your original code didn't work: #

You likely only added the SCIMultiSurfaceModifier to one surface, or you tried to retrieve a per-surface modifier instead of letting the multi-surface wrapper handle synchronization. The SCIMultiSurfaceModifier is designed to propagate gesture events and cursor state across all surfaces it's attached to, so adding it to every surface is critical.

If you need to sync cursor position manually (for example, with the long press gesture from the first section), you can loop through all surfaces and update their cursor modifiers:

- (void)syncCursorAcrossSurfaces:(CGPoint)location {
    for (SCIChartSurface *surface in yourArrayOfSurfaces) {
        MHSCICursorModifier *cursor = nil;
        for (id<ISCIChartModifier> modifier in surface.chartModifiers) {
            if ([modifier isKindOfClass:[MHSCICursorModifier class]]) {
                cursor = (MHSCICursorModifier *)modifier;
                break;
            }
        }
        if (cursor) {
            [cursor showCursorAt:location];
        }
    }
}

Call this method from your gesture handler whenever the cursor position updates to ensure all surfaces show the same cursor location.

内容的提问来源于stack exchange，提问作者Chris