Make the QR Code scanner caption fit on multiple lines.

ios/chrome/browser/ui/qr_scanner/qr_scanner_view.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/qr_scanner/qr_scanner_view.h"
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
 #include "ios/chrome/browser/ui/icons/chrome_icon.h"
@@ skipping 23 matching lines @@
 
 // Corner radius of the border around the viewport.
 const CGFloat kViewportBorderCornerRadius = 2.0;
 // Line width of the viewport border.
 const CGFloat kViewportBorderLineWidth = 4.0;
 // Shadow opacity of the viewport border.
 const CGFloat kViewportBorderShadowOpacity = 1.0;
 // Shadow radius of the viewport border.
 const CGFloat kViewportBorderShadowRadius = 10.0;
 // Padding of the viewport caption, below the viewport.
-const CGFloat kViewportCaptionPadding = 24.0;
+const CGFloat kViewportCaptionVerticalPadding = 14.0;
+// Padding of the viewport caption from the edges of the superview.
+const CGFloat kViewportCaptionHorizontalPadding = 20.0;
 // Shadow opacity of the viewport caption.
 const CGFloat kViewportCaptionShadowOpacity = 1.0;
 // Shadow radius of the viewport caption.
 const CGFloat kViewportCaptionShadowRadius = 5.0;
 
 // Duration of the flash animation played when a code is scanned.
 const CGFloat kFlashDuration = 0.5;
 
 // Returns a square of size |rectSize| centered inside |frameSize|.
 CGRect CenteredRectForViewport(CGSize frameSize, CGFloat rectSize) {
@@ skipping 408 matching lines @@
                                                   constant:-kButtonPadding],
     [[_torchButton bottomAnchor] constraintEqualToAnchor:[self bottomAnchor]
                                                 constant:-kButtonPadding]
   ]];
 }
 
 - (void)addViewportCaptionLabel {
   UILabel* viewportCaption = [[[UILabel alloc] init] autorelease];
   NSString* label = l10n_util::GetNSString(IDS_IOS_QR_SCANNER_VIEWPORT_CAPTION);
   [viewportCaption setText:label];
+  [viewportCaption setNumberOfLines:0];
+  [viewportCaption setTextAlignment:NSTextAlignmentCenter];
   [viewportCaption setAccessibilityLabel:label];
   [viewportCaption setAccessibilityIdentifier:@"qr_scanner_viewport_caption"];
   [viewportCaption setTextColor:[UIColor whiteColor]];
   [viewportCaption.layer setShadowColor:[UIColor blackColor].CGColor];
   [viewportCaption.layer setShadowOffset:CGSizeZero];
   [viewportCaption.layer setShadowRadius:kViewportCaptionShadowRadius];
   [viewportCaption.layer setShadowOpacity:kViewportCaptionShadowOpacity];
   [viewportCaption.layer setMasksToBounds:NO];
   [viewportCaption.layer setShouldRasterize:YES];
   [self addSubview:viewportCaption];
 
   // Constraints for viewportCaption.
   [viewportCaption setTranslatesAutoresizingMaskIntoConstraints:NO];
   [NSLayoutConstraint activateConstraints:@[
-    [[viewportCaption centerXAnchor]
-        constraintEqualToAnchor:[self centerXAnchor]],
-    [[viewportCaption centerYAnchor]
+    [[viewportCaption topAnchor]
         constraintEqualToAnchor:[self centerYAnchor]
-                       constant:GetViewportSize() / 2 + kViewportCaptionPadding]
+                       constant:GetViewportSize() / 2 +
+                                kViewportCaptionVerticalPadding],
+    [viewportCaption.leftAnchor

[gambard, 2017/02/22 12:43:48]

I am not sure about how left/right anchor are treated in RTL. Maybe
trailing/leading would be safer?

[jif, 2017/02/22 12:59:07]

Done.

+        constraintEqualToAnchor:self.leftAnchor
+                       constant:kViewportCaptionHorizontalPadding],
+    [viewportCaption.rightAnchor
+        constraintEqualToAnchor:self.rightAnchor
+                       constant:-kViewportCaptionHorizontalPadding],
   ]];
 }
 
 - (void)setupPreviewView {
   DCHECK(!_previewView);
   _previewView.reset([[VideoPreviewView alloc] initWithFrame:self.frame]);
   [self insertSubview:_previewView atIndex:0];
 }
 
 - (void)setupPreviewOverlayView {
@@ skipping 30 matching lines @@
   [NSLayoutConstraint activateConstraints:@[
     [[_previewOverlay centerXAnchor]
         constraintEqualToAnchor:[self centerXAnchor]],
     [[_previewOverlay centerYAnchor]
         constraintEqualToAnchor:[self centerYAnchor]],
     _overlaySquareConstraint, _overlayWidthConstraint, _overlayHeightConstraint
   ]];
 }
 
 @end