[docs] UIKit.md: Views & Controls section

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Daniel Arantes Loverde
2026-08-29 19:32:31 -03:00
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## Views & Controls
<!-- batch 10 -->
<details>
<summary><b>UIButton</b> — per-state accessors, all-state setters</summary>
### Per-state properties
`imageForNormal` / `imageForHighlighted` / `imageForSelected` / `imageForDisabled`,
`titleForNormal` / `…Highlighted` / `…Selected` / `…Disabled`,
`titleColorForNormal` / `…Highlighted` / `…Selected` / `…Disabled` — get/set
shortcuts for the matching `UIControl.State` (also `@IBInspectable`).
```swift
button.titleForNormal = "Save"
button.titleColorForDisabled = .tertiaryLabel
```
### `func setTitleForAllStates(_:)` / `func setTitleColorForAllStates(_:)` / `func setImageForAllStates(_:)`
Apply one value to `.normal`, `.selected`, `.highlighted`, `.disabled` at once.
```swift
button.setTitleColorForAllStates(.white)
```
### `func centerTextAndImage(spacing: CGFloat)`
Balance title/image edge insets so text + icon sit centred with `spacing` between them.
```swift
button.centerTextAndImage(spacing: 8)
```
</details>
<details>
<summary><b>UILabel</b></summary>
### `func lineNumbers() -> Int`
Rendered line count at the current width.
```swift
if bodyLabel.lineNumbers() > 3 { showMoreButton() }
```
### `var getEstimatedHeight: CGFloat`
Height the label would need to show its full text/attributed text unclipped.
</details>
<details>
<summary><b>UITextField</b></summary>
### `var placeholderColor: UIColor`
Get/set the placeholder text colour (rebuilds `attributedPlaceholder`; setter is a
no-op if no placeholder text is set).
```swift
field.placeholder = "Email"
field.placeholderColor = .secondaryLabel
```
### `func addPaddingLeft(_ padding: CGFloat)`
Inset the text from the left with an empty spacer view.
### `func addPaddingLeftIcon(_ image: UIImage, padding: CGFloat)`
Left view = an icon plus trailing padding.
```swift
field.addPaddingLeftIcon(UIImage(systemName: "magnifyingglass")!, padding: 8)
```
</details>
<details>
<summary><b>UIImageView</b> (<code>@MainActor</code>)</summary>
### `func changeColorOfImage(_ color: UIColor, image: UIImage?) -> UIImageView`
Set a template-rendered image tinted to `color`; returns `self`.
```swift
iconView.changeColorOfImage(.systemBlue, image: UIImage(named: "star"))
```
### `var encodeToBase64: String?`
JPEG (quality 0.6) of the current image as a Base64 string.
### `func addAspectRatioConstraint()` / `func removeAspectRatioConstraint()`
Add / remove a width-to-height constraint matching the current image's ratio.
```swift
photoView.image = photo
photoView.addAspectRatioConstraint()
```
</details>
<details>
<summary><b>UIImage</b> — recolour, resize, thumbnails, masks, init</summary>
### `func imageWithColor(color: UIColor) -> UIImage` / `func tintImage(color: UIColor) -> UIImage`
Return a copy filled / tinted with `color` (keeps the alpha shape).
```swift
let redIcon = icon.tintImage(color: .systemRed)
```
### `func backgroundColorTransparent(initialColor: UIColor, finalColor: UIColor) -> UIImage?`
Make pixels in a colour range transparent.
### `class func outlinedEllipse(size: CGSize, color: UIColor, lineWidth: CGFloat = 1) -> UIImage?`
Generate a stroked-ellipse image.
```swift
UIImage.outlinedEllipse(size: CGSize(width: 24, height: 24), color: .label)
```
### `func resizeImage(newWidth: CGFloat) -> UIImage`
Scale to `newWidth`, keeping the aspect ratio.
### `func createThumbnail(_ maxPixelSize: UInt) -> UIImage`
Fast down-sampled thumbnail via `CGImageSource`.
```swift
let thumb = fullImage.createThumbnail(200)
```
### `func maskWithAlphaImage(maskImage: UIImage) -> UIImage`
Use another image's alpha as a mask.
### `func isAnimated() -> Bool`
Whether the image has more than one frame.
### `init?(base64String: String, scale: CGFloat = 1)`
Decode a Base64 string to an image.
### `init(view: UIView)` — *`@MainActor`*
Rasterise a view into an image.
```swift
let snapshot = UIImage(view: cardView)
```
</details>
<details>
<summary><b>UIColor</b> — hex, components</summary>
### `convenience init(hex: String)`
Parse `#RGB`, `#RGBA`, `#RRGGBB`, or `#RRGGBBAA` (with or without `#`).
```swift
view.backgroundColor = UIColor(hex: "#1E88E5")
UIColor(hex: "FF0000CC") // red at 80% alpha
```
### `var hexString: String?`
`#RRGGBB` (or `#RRGGBBAA` when alpha < 1).
### `var redValue` / `var greenValue` / `var blueValue` / `var alphaValue`
Individual channel values (`CGFloat`, via `CIColor`).
```swift
UIColor.systemBlue.redValue // 0.01.0
```
</details>
<details>
<summary><b>UIScrollView</b> — snapshot, visible rect, paged scrolling</summary>
### `var snapshot: UIImage?`
Image of the **entire** content size (not just the visible part) — works on
`UITableView` / `UICollectionView` too.
### `var visibleRect: CGRect`
The currently visible content region.
### `var offsetInPage: CGFloat`
Fractional position within the current page height (`0.0``1.0`).
### `func scrollUp(animated:)` / `scrollDown(animated:)` / `scrollLeft(animated:)` / `scrollRight(animated:)`
Move one page (respects `isPagingEnabled`). `animated` defaults to `true`.
```swift
nextButton.onTap = { scrollView.scrollRight() }
```
### `enum orientation`
`horizontal` / `vertical` — helper enum used by scroll utilities.
</details>
<details>
<summary><b>UITapGestureRecognizer</b></summary>
### `func didTapAttributedTextInLabel(label: UILabel, textToTouch: String) -> Bool`
Whether the tap landed on a given substring of a label's attributed text — for
making part of a label tappable.
```swift
@objc func handleTap(_ g: UITapGestureRecognizer) {
if g.didTapAttributedTextInLabel(label: termsLabel, textToTouch: "Terms of Use") {
openTerms()
}
}
```
</details>
## Navigation & Controllers