[ios]Add a maximumWidthRatio property to customize maximum width of scale bar.

platform/ios/CHANGELOG.md

@@ -5,6 +5,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 ## master
 
 * Fix ornaments' view constraints bug when devices change to bold-text mode. ([#57](https://github.com/mapbox/mapbox-gl-native-ios/pull/57))
+* Add a `maximumWidthRatio` property for customizing maximum width of scale bar. ([#65](https://github.com/mapbox/mapbox-gl-native-ios/pull/65))
 
 ## 5.5.0 - November 5, 2019
 

platform/ios/src/MGLMapView.h

@@ -329,6 +329,13 @@ MGL_EXPORT
  */
 @property (nonatomic, assign) CGPoint scaleBarMargins;
 
+/**
+ The maximum width ratio of the scale bar relative to the map view's frame.
+ This value is limited from 0.1 to 1.
+ Default is 0.5(half of map view's width).
+ */
+@property (nonatomic, assign) CGFloat scaleBarMaximumWidthRatio;
+
 /**
  A control indicating the map’s direction and allowing the user to manipulate
  the direction, positioned in the upper-right corner.

platform/ios/src/MGLMapView.mm

@@ -576,6 +576,7 @@ - (void)commonInit
     _scaleBarConstraints = [NSMutableArray array];
     _scaleBarPosition = MGLOrnamentPositionTopLeft;
     _scaleBarMargins = MGLOrnamentDefaultPositionOffset;
+    _scaleBar.margins = MGLOrnamentDefaultPositionOffset;
 
     [self installConstraints];
 
@@ -800,9 +801,20 @@ - (void)setScaleBarPosition:(MGLOrnamentPosition)scaleBarPosition {
 - (void)setScaleBarMargins:(CGPoint)scaleBarMargins {
     MGLLogDebug(@"Setting scaleBarMargins: (x:%f, y:%f)", scaleBarMargins.x, scaleBarMargins.y);
     _scaleBarMargins = scaleBarMargins;
+    if([self.scaleBar isKindOfClass:[MGLScaleBar class]]) {
+        ((MGLScaleBar *)self.scaleBar).margins = scaleBarMargins;
+    }
     [self installScaleBarConstraints];
 }
 
+- (void)setScaleBarMaximumWidthRatio:(CGFloat)scaleBarMaximumWidthRatio {
+    _scaleBarMaximumWidthRatio = scaleBarMaximumWidthRatio;
+    if([self.scaleBar isKindOfClass:[MGLScaleBar class]]) {
+        ((MGLScaleBar *)self.scaleBar).maximumWidthRatio = scaleBarMaximumWidthRatio;
+    }
+    [self updateScaleBar];
+}
+
 - (void)setCompassViewPosition:(MGLOrnamentPosition)compassViewPosition {
     MGLLogDebug(@"Setting compassViewPosition: %lu", compassViewPosition);
     _compassViewPosition = compassViewPosition;

platform/ios/src/MGLScaleBar.h

@@ -6,4 +6,13 @@
 // Sets the scale and redraws the scale bar
 @property (nonatomic, assign) CLLocationDistance metersPerPoint;
 
+/*
+    The maximum width ratio of the scale bar relative to the map view's frame.
+    This value is limited from 0.1 to 1.
+    Default is 0.5(half of map view's width).
+ */
+@property (nonatomic, assign) CGFloat maximumWidthRatio;
+
+@property (nonatomic, assign) CGPoint margins;
+
 @end

platform/ios/src/MGLScaleBar.mm

@@ -142,6 +142,7 @@ - (instancetype)initWithFrame:(CGRect)frame {
 
 - (void)commonInit {
     _size = CGSizeZero;
+    _maximumWidthRatio = 0.5;
 
     _primaryColor = [UIColor colorWithRed:18.0/255.0 green:45.0/255.0 blue:17.0/255.0 alpha:1];
     _secondaryColor = [UIColor colorWithRed:247.0/255.0 green:247.0/255.0 blue:247.0/255.0 alpha:1];
@@ -229,7 +230,25 @@ - (CGFloat)actualWidth {
 - (CGFloat)maximumWidth {
     // TODO: Consider taking Scale Bar margins into account here.
     CGFloat fullWidth = CGRectGetWidth(self.superview.bounds);
-    return floorf(fullWidth / 2);
+
+    if(self.maximumWidthRatio < 0.1) {
+        self.maximumWidthRatio = 0.1;
+    }
+    else if (self.maximumWidthRatio > 1) {
+        self.maximumWidthRatio = 1;
+    }
+
+    CGFloat result = floorf(fullWidth * self.maximumWidthRatio);
+    return result > fullWidth - (self.margins.x * 2) ? fullWidth - (self.margins.x * 2) : result;
+}
+
+- (void)setMaximumWidthRatio:(CGFloat)maximumWidthRatio {
+    _maximumWidthRatio = maximumWidthRatio;
+
+    [self updateVisibility];
+
+    self.recalculateSize = YES;
+    [self invalidateIntrinsicContentSize];
 }
 
 - (CGFloat)unitsPerPoint {