Expose TextLayoutResult APIs for accurately reading line metrics [237428541]

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Feature Request

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Description

sa...@squareup.com

created issue #1

Jun 28, 2022 08:24PM

It is currently difficult to draw custom spans for Text() because TextLayoutResult does not expose any APIs for accurately reading line bounds. Considering that AndroidParagraph already has APIs such as getLineAscent(), getLineBaseline() and getLineDescent(), can they be bubbled up to TextLayoutResult?

Having access to getTopPadding() and getBottomPadding() from android.text.Layout would also be helpful.

AFAIK, there is currently no workaround for reading these values. Inspecting font metrics would have been one option, but that is not available either (https://issuetracker.google.com/issues/173648606).

- Jetpack Compose version: 1.2.0-rc02
- Jetpack Compose component used: Text

Comments

ha...@google.com <ha...@google.com> Oct 6, 2022 08:48AM

Reassigned to ha...@google.com.

ja...@squareup.com <ja...@squareup.com> #2Apr 27, 2023 05:54PM

Project: platform/frameworks/support
Branch: androidx-master-dev

commit c60f33e229e31ab328ef6b59dab63b264954831c
Author: Alexandre Elias <aelias@google.com>
Date: Fri Jul 10 16:23:09 2020

Semantics no-op cleanups

Partly in response to lmr's broad code review, I did a pass of
superficial API/implementation cleanup. The main changes are:

- I changed each Boolean SemanticsProperty where false is equivalent to
not being present to take "Unit" instead. This is conceptually
clearer: it avoids questions like "can I cancel out a semantics from a
merged child by setting it to false?" Because "property = Unit" looks
weird, I also changed the style of these to "property()".

- I moved the Semantics id generator closer to where it's used, in
SemanticsModifierCore. I made it internal and an AtomicInt.
(Note that integer ids are heavily used in the Android
AccessibilityNodeInfo APIs so I can't simply remove them entirely.)

- I deleted dead code. Some examples include SemanticsHintOverrides,
a public API not connected to anything, and SemanticsPropertyKey
merge() open method which is never called. (In both cases I have
a different plan in mind for accessibility.)

Fixes: 145951226
Fixes: 145955412
Test: existing tests
Relnote: "Single-value semantics properties now use a calling style.
For example, 'semantics { hidden = true }' is now written as:
'semantics { hidden() }'."

Change-Id: Ic1afd12ea22c926babc9662f1804d80b33aa0cfc

M ui/integration-tests/benchmark/src/androidTest/java/androidx/ui/benchmark/test/LayoutNodeModifierBenchmark.kt
M ui/ui-core/api/0.1.0-dev15.txt
M ui/ui-core/api/current.txt
M ui/ui-core/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-core/api/public_plus_experimental_current.txt
M ui/ui-core/api/restricted_0.1.0-dev15.txt
M ui/ui-core/api/restricted_current.txt
M ui/ui-core/src/androidAndroidTest/kotlin/androidx/ui/graphics/vector/VectorTest.kt
M ui/ui-core/src/androidAndroidTest/kotlin/androidx/ui/semantics/SemanticsTests.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidActuals.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidComposeView.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidComposeViewAccessibilityDelegateCompat.kt
M ui/ui-core/src/androidMain/kotlin/androidx/ui/core/AndroidPopup.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/Expect.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsConfiguration.kt
D ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsHintOverrides.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsModifier.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsNode.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsOwner.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/core/semantics/SemanticsWrapper.kt
M ui/ui-core/src/commonMain/kotlin/androidx/ui/semantics/SemanticsProperties.kt
M ui/ui-foundation/api/0.1.0-dev15.txt
M ui/ui-foundation/api/current.txt
M ui/ui-foundation/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-foundation/api/public_plus_experimental_current.txt
M ui/ui-foundation/api/restricted_0.1.0-dev15.txt
M ui/ui-foundation/api/restricted_current.txt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Clickable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Dialog.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/Scroller.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/selection/Selectable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/selection/Toggleable.kt
M ui/ui-foundation/src/main/java/androidx/ui/foundation/semantics/FoundationSemanticsProperties.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ButtonTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/CardTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/CheckboxScreenshotTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/RadioButtonScreenshotTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ScaffoldTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/SnackbarTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/SurfaceTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/ripple/RippleIndicationTest.kt
M ui/ui-material/src/androidTest/java/androidx/ui/material/textfield/TextFieldScreenshotTest.kt
M ui/ui-material/src/main/java/androidx/ui/material/AppBar.kt
M ui/ui-material/src/main/java/androidx/ui/material/TextFieldImpl.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/AssertsTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/CallSemanticsActionTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/ErrorMessagesTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/FindersTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/PrintToStringTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/ScrollToTest.kt
M ui/ui-test/src/androidTest/java/androidx/ui/test/TextActionsTest.kt
M ui/ui-test/src/main/java/androidx/ui/test/Actions.kt
M ui/ui-test/src/main/java/androidx/ui/test/Filters.kt
M ui/ui-text/api/0.1.0-dev15.txt
M ui/ui-text/api/current.txt
M ui/ui-text/api/public_plus_experimental_0.1.0-dev15.txt
M ui/ui-text/api/public_plus_experimental_current.txt
M ui/ui-text/api/restricted_0.1.0-dev15.txt
M ui/ui-text/api/restricted_current.txt
M ui/ui-text/src/commonMain/kotlin/androidx/ui/text/CoreTextField.kt
M ui/ui-text/src/commonMain/kotlin/androidx/ui/text/TextSemanticsProperties.kt

https://android-review.googlesource.com/1360099

ha...@google.com <ha...@google.com> #3Apr 28, 2023 12:14PM

Ascent and Descent values in the context of text layout are slightly different from what they signify in font metrics.

Top, ascent, descent, bottom values anchored around (baseline = 0) can be calculated for a Paint object because it only has a single configuration for textSize, typeface, font settings, etc. that affect font metrics. However, a text layout (vertically placed lines of text) may have varying range of text sizes, typefaces, etc on a single line. Hence, it can be conceptually impossible to say what is ascent or descent of a text line since these values can fluctuate between individual characters on a line.

Ascent and Descent are still provided by android.text.Layout, android.text.StaticLayout but in a different way. Ascent refers to the difference between top and baseline, while Descent refers to the difference between bottom and baseline. You can actually see how these values are calculated here https://cs.android.com/android/platform/superproject/+/refs/heads/master:frameworks/base/core/java/android/text/Layout.java;l=1749-1778

If you want to have access to getLineAscent and getLineDescent from StaticLayout(Paragraph in Compose), you can easily calculate those values via

getLineDescent(x) = getLineBottom(x) - getLineBaseline(x)
getLineAscent(x) = getLineTop(x) - getLineBaseline(x)

On the other hand, we can discuss the practicality of exposing some of these values (b/173648606) from AndroidTextPaint#fontMetrics in AndroidParagraph (both are internal). It only makes sense to read those fontMetrics if;

Your text layout contains only a single paragraph
That paragraph has no spans that affect font metrics

Message last modified on Apr 28, 2023 01:36PM

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ap...@google.com <ap...@google.com> #4Feb 14, 2024 01:51PM

Project: platform/frameworks/support
Branch: androidx-main

commit c652a36a7fd43af14820497b1efa3215b7424f8d
Author: Anastasia Soboleva <soboleva@google.com>
Date: Fri Feb 09 12:08:13 2024

Add getBaseline to TextLayoutResult

Fixes: 324417208
Bug: 237428541

Test: added new tests to cover the functionality

Relnote: "The TextLayoutResult now exposes the `getLineBaseline(lineIndex)` method. This allows to read the baseline of an arbitrary line of the text in addition to existing convenience properties `firstBaseline` and `lastBaseline`"
Change-Id: Ide4e848470681364cdf7e141154d8fe5b7641eb9

M compose/ui/ui-text/api/current.ignore
M compose/ui/ui-text/api/current.txt
M compose/ui/ui-text/api/restricted_current.ignore
M compose/ui/ui-text/api/restricted_current.txt
M compose/ui/ui-text/src/androidInstrumentedTest/kotlin/androidx/compose/ui/text/MultiParagraphIntegrationTest.kt
M compose/ui/ui-text/src/androidInstrumentedTest/kotlin/androidx/compose/ui/text/ParagraphIntegrationTest.kt
M compose/ui/ui-text/src/androidMain/kotlin/androidx/compose/ui/text/AndroidParagraph.android.kt
M compose/ui/ui-text/src/androidMain/kotlin/androidx/compose/ui/text/Paragraph.android.kt
M compose/ui/ui-text/src/commonMain/kotlin/androidx/compose/ui/text/MultiParagraph.kt
M compose/ui/ui-text/src/commonMain/kotlin/androidx/compose/ui/text/Paragraph.kt
M compose/ui/ui-text/src/commonMain/kotlin/androidx/compose/ui/text/TextLayoutResult.kt
M compose/ui/ui-text/src/desktopTest/kotlin/androidx/compose/ui/text/DesktopParagraphTest.kt
M compose/ui/ui-text/src/skikoMain/kotlin/androidx/compose/ui/text/Paragraph.skiko.kt
M compose/ui/ui-text/src/skikoMain/kotlin/androidx/compose/ui/text/SkiaParagraph.skiko.kt

https://android-review.googlesource.com/2952738

ha...@google.com <ha...@google.com> May 29, 2024 12:03AM

Reassigned to an...@google.com.

Issue 237428541