LIVE-225: Add left button image and text support

https://github.com/slackhq/SlackTextViewController/pull/654/files

Author: Henrique Valcanaia

Source/SLKTextInputbar.m

@@ -105,6 +105,8 @@ - (void)slk_commonInit
 
     [self slk_registerTo:self.layer forSelector:@selector(position)];
     [self slk_registerTo:self.leftButton.imageView forSelector:@selector(image)];
+    [self slk_registerTo:self.leftButton.titleLabel forSelector:@selector(font)];
+    [self slk_registerTo:self.leftButton.titleLabel forSelector:@selector(text)];
     [self slk_registerTo:self.rightButton.titleLabel forSelector:@selector(font)];
 }
 
@@ -746,7 +748,7 @@ - (void)slk_updateConstraintConstants
     else {
         self.editorContentViewHC.constant = zero;
 
-        CGSize leftButtonSize = [self.leftButton imageForState:self.leftButton.state].size;
+        CGSize leftButtonSize = self.leftButton.intrinsicContentSize;
 
         if (leftButtonSize.width > 0) {
             self.leftButtonHC.constant = roundf(leftButtonSize.height);
@@ -802,6 +804,11 @@ - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(N
             [self slk_updateConstraintConstants];
         }
     }
+    else if ([object isEqual:self.leftButton.titleLabel] &&
+             ([keyPath isEqualToString:NSStringFromSelector(@selector(font))]
+              || [keyPath isEqualToString:NSStringFromSelector(@selector(text))])) {
+        [self slk_updateConstraintConstants];
+    }
     else if ([object isEqual:self.rightButton.titleLabel] && [keyPath isEqualToString:NSStringFromSelector(@selector(font))]) {
 
         [self slk_updateConstraintConstants];
@@ -839,6 +846,8 @@ - (void)dealloc
 
     [self slk_unregisterFrom:self.layer forSelector:@selector(position)];
     [self slk_unregisterFrom:self.leftButton.imageView forSelector:@selector(image)];
+    [self slk_unregisterFrom:self.leftButton.titleLabel forSelector:@selector(font)];
+    [self slk_unregisterFrom:self.leftButton.titleLabel forSelector:@selector(text)];
     [self slk_unregisterFrom:self.rightButton.titleLabel forSelector:@selector(font)];
 }