[FEAT] View/lineLimit modifier by MiaKoring · Pull Request #440 · moreSwift/swift-cross-ui

MiaKoring · 2026-02-09T20:15:26Z

Resolves #432

Summary

Adds the View/lineLimit modifier, allowing to limit the vertical space a Text is allowed to occupy based on the amount of lines instead of fixed pixel values.

Support:

AppKitBackend
UIKitBackend
WinUIBackend
GtkBackend

Changes

added View/lineLimit modifier
added Environment/lineLimitSettings containing the lineLimit number and wether space should be reserved
added Environment/lineLimit computed Int? to match SwiftUI’s counterpart for usage in @Environment, setting is not supported, as I see clearness issues when it gets set without LineLimit/reservesSpace

Improvements

WinUI doesn’t require the single line height measurement anymore, as it now follows the SCUI dictated lineHeight of resolvedFont

Problems

On GtkBackend there is the issue that we can’t set the lineHeight, therefore its not immediately possible to calculate the height of Text if it had n lines.

I took the approach WinUI used before of just measuring another widget:
I create a multiline string with as many lines as lineLimit specifies and measure it inside a dedicated measurement widget that gets created at the start of the apps main loop.

Updating the widget and measuring it only happens when lineLimit is set in the environment, therefore not affecting performance unless used. lineLimit should also mostly get used with smaller numbers, so generating the string shouldn’t have too much of a performance impact

There are further issues when Text is rendered inside a ScrollView, detailed in #438

Notes

The changes can be tested using Examples/LineLimitTest, I see no point in keeping it around, so it should be removed before merging.

This PR is built on top of #430
It should be merged first. This one is marked as draft until then.

@entry

ControlsExample now uses @entry

# Conflicts: # Sources/SwiftCrossUI/Environment/EnvironmentValues.swift # Sources/SwiftCrossUI/State/AppStorage.swift # Sources/SwiftCrossUIMacrosPlugin/EntryMacro.swift # Sources/SwiftCrossUIMacrosPlugin/Utils/VariableExtension.swift # Tests/SwiftCrossUITests/EntryMacroTests.swift

stackotter · 2026-02-23T00:51:31Z

Examples/Bundler.toml

 product = 'ColorsExample'
 version = '0.1.0'
+
+[apps.LineLimitTest]


As you mentioned in the PR description, this should be removed before merging

stackotter · 2026-02-23T00:53:26Z

Sources/AppKitBackend/AppKitBackend.swift

            attributes: Self.attributes(forTextIn: environment)
        )
+
+        var usedHeight = rect.size.height


Rename this to height (as you later set it to not be the used height, but rather the height imposed by SCUI).

stackotter · 2026-02-23T00:53:51Z

Sources/AppKitBackend/AppKitBackend.swift

+        var usedHeight = rect.size.height
+
+        if let lineLimitSettings = environment.lineLimitSettings {
+            let height =


Rename this to limitedHeight to not clash with the other variable rename

stackotter · 2026-02-23T01:53:48Z

Sources/SwiftCrossUI/Environment/EnvironmentValues.swift

    /// Whether user interaction is enabled. Set by ``View/disabled(_:)``.
    @Entry public var isEnabled: Bool = true
+
+    @Entry public var lineLimitSettings: LineLimit?


Document this

stackotter · 2026-02-23T01:54:25Z

Sources/SwiftCrossUI/State/StateImpl.swift

@@ -1,4 +1,4 @@
-struct StateImpl<Storage: StateStorageProtocol> {
+public struct StateImpl<Storage: StateStorageProtocol> {


Make these internal again unless necessary (I think this may just be from a merging issue given that you changed this in an earlier pr?)

yes removing the public keyword again worked without any warnings, curious that it was still here tho, I’m pretty sure the commit removing it was newer. anyway, its gone again

stackotter · 2026-02-23T02:05:52Z

Sources/UIKitBackend/UIKitBackend+Passive.swift

            context: nil
        )
+
+        var usedHeight = size.height


Similar to AppKitBackend, rename this var to height, and rename height (in the if) to limitedHeight

stackotter · 2026-02-23T02:10:33Z

Sources/GtkBackend/GtkBackend.swift

+            )
+
+            let pango = Pango(for: measurementCustomLabel)
+            let (_, potentialHeight) = pango.getTextSize(


Rename potentialHeight to heightLimit

stackotter · 2026-02-23T02:12:55Z

Sources/GtkBackend/GtkBackend.swift

+        var usedHeight = height
+
+        if let lineLimitSettings = environment.lineLimitSettings {
+            let multilineString = [String](repeating: "a", count: lineLimitSettings.limit)


Is it possible for us to instead just measure a single "a" and then multiply the resulting height by the line limit? It'd be worth trying if you haven't already because it should be more efficient (don't need to construct a string and don't have to lay out as much).

It is not, as gtk currently doesn’t respect the lineHeight.
the height of a single line of “a” * 2 is not the same as “a\na” due to some spacing(or smth like that) in between lines.
Once lineHeight is properly respected it would be a yes.

Note that the actual baseline-to-baseline distance between lines of text is influenced by other factors, such as pango_layout_set_spacing() and pango_layout_set_line_spacing().

Just found that in the get_line_height docs. Might help resolve that

doesn’t work

public func getLineHeight(_ text: String) -> Double { let layout = pango_layout_new(pangoContext)! pango_layout_set_text(layout, text, Int32(text.utf8.count)) let line = pango_layout_get_line(layout, 0) var height: Int32 = 0 pango_layout_line_get_height(line, &height) g_object_unref(UnsafeMutableRawPointer(layout)) return pango_units_to_double(height) }

using this * lineLimit leads to

(expected would be 1, 2, 3, 4)

Ah I didn’t mean to use that function, because that would just return what the line height was set to. But the docs mention ‘baseline to baseline distance’ which is what SwiftCrossUI refers to as line height. They say that you need to incorporate the pango spacing and line spacing in order to compute that distance we want.

should we just pango_layout_set_spacing for text in general to 0 to match the other platforms? And later allow custom line spacing via a https://developer.apple.com/documentation/swiftui/view/linespacing(_:)

gtk documentation says linespacing and spacing are 0 by default. huh?

why doesn't it match then?

Weird… might be worth double checking just in case

Can confirm, both are 0

stackotter · 2026-02-23T02:19:28Z

Sources/GtkBackend/GtkBackend.swift

+                multilineString,
+                ellipsize: (widget as! CustomLabel).ellipsize,
+                proposedWidth: proposedWidth.map(Double.init),
+                proposedHeight: proposedHeight.map(Double.init)


Have you tested this fully on Linux? It seems that reservesSpace = true would not function correctly due to the text getting ellipsized. You should set proposedWidth and proposedHeight to nil instead because we just want to know the ideal size of the measurement string (we don't want line wrapping or ellipsizing to happen).

True, with proposedWidth/Height it can get squished. Setting to nil prevents it like you expected. And yes, I forgot test this case on GtkBackend, I’m sorry.
Still something wrong with the alignment, as it shouldn't be centered. Any idea how to prevent it? My brain isn’t really functioning well today

vertical alignment now works after settign textView.yalign = 0.0 in the create function

No worries about not testing it, it’s easy to miss stuff when you have to test it lots of times during development

stackotter · 2026-02-23T02:21:23Z

Sources/GtkBackend/GtkBackend.swift

        )
-        return SIMD2(width, height)
+
+        var usedHeight = height


Maybe rename to imposedHeight or something similar. To me usedHeight sounds like the height that the text used, rather than the height that we are going to use as our return value (which I assume is what you meant?)

MiaKoring added 11 commits February 6, 2026 18:48

added @entry for EnvironmentValues

f087341

Added @AppStorage Support, updated ControlsExample, added Test

1834783

ControlsExample now uses @entry

Made EnvironmentValues @entry

c96e66f

LineLimit support on AppKitBackend

d4820c2

Added Support for UIKit

aa1cb1c

Addded flawed Gtk Support

059c3a5

Added WinUI Support

a45c6f0

applied format_and_lint

9d1d32e

removed single line measurement on WinUI backend

e8809e4

fixed WinUI compile failure

b8a2b06

Gtk now fully supported

e6a3ddf

MiaKoring marked this pull request as draft February 9, 2026 20:15

MiaKoring mentioned this pull request Feb 14, 2026

Text() doesn’t wrap inside ScrollView() on GtkBackend #438

Open

MiaKoring marked this pull request as ready for review February 16, 2026 14:14

stackotter requested changes Feb 23, 2026

View reviewed changes

MiaKoring added 3 commits February 23, 2026 15:03

Merge branch 'main' into feat/lineLimit

6816005

Adressed requested changes

2a9ecaf

Merge branch 'main' into feat/lineLimit

bca3601

		@@ -1,4 +1,4 @@
		struct StateImpl<Storage: StateStorageProtocol> {
		public struct StateImpl<Storage: StateStorageProtocol> {

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MiaKoring commented Feb 9, 2026 •

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