starred/terminal
1
0
Fork 0
mirror of https://github.com/microsoft/terminal.git synced 2026-02-03 21:25:34 +00:00
Code Issues 19.0k Packages Projects Releases 20 Wiki Activity

Consider performing font fallback analysis only if the chosen font is not adequate #14769

New Issue
Open
opened 2026-01-31 04:19:02 +00:00 by claunia · 2 comments
claunia commented 2026-01-31 04:19:02 +00:00
Owner
Copy Link

Originally created by @skyline75489 on GitHub (Aug 3, 2021).

Description of the new feature/enhancement

Right now the _AnalyzeFontFallback is always called if the text is "complex":

e7108332f7/src/renderer/dx/CustomTextLayout.cpp (L246-L247)

We already know that even for pure ASCII characters, some fonts will treat them as "complex". But the real need for font fallback emerges only when the font don't actually contains the needed glyph. For example when dealing with "ABC中文". You have to find "Microsoft YaHei" as fallback, otherwise "中文" is nowhere to be find in "Cascadia Code“.

Proposed technical implementation details (optional)

To avoid the unnecessary overhead of finding fallbacks (MapCharacters, which is relatively expensive), my proposed solution is to delay the fallback analysis and put it in _ShapeGlyphRun. Inside _ShapeGlyphRun, the method GetGlyphs will tell you precisely if there are available glyphs inside the desired font (_glyphIndices):

e7108332f7/src/renderer/dx/CustomTextLayout.cpp (L414)

If no glyphs can be found (which I assume is a rather rare case), then the fallback analysis is necessary.

Originally created by @skyline75489 on GitHub (Aug 3, 2021). # Description of the new feature/enhancement Right now the `_AnalyzeFontFallback` is always called if the text is "complex": https://github.com/microsoft/terminal/blob/e7108332f72a3c14c72a65484d091c4e79ab28b2/src/renderer/dx/CustomTextLayout.cpp#L246-L247 We already know that even for pure ASCII characters, some fonts will treat them as "complex". But the real need for font fallback emerges *only* when the font don't actually contains the needed glyph. For example when dealing with "ABC中文". You have to find "Microsoft YaHei" as fallback, otherwise "中文" is nowhere to be find in "Cascadia Code“. # Proposed technical implementation details (optional) To avoid the unnecessary overhead of finding fallbacks (`MapCharacters`, which is relatively expensive), my proposed solution is to delay the fallback analysis and put it in `_ShapeGlyphRun`. Inside `_ShapeGlyphRun`, the method `GetGlyphs` will tell you precisely if there are available glyphs inside the desired font (`_glyphIndices`): https://github.com/microsoft/terminal/blob/e7108332f72a3c14c72a65484d091c4e79ab28b2/src/renderer/dx/CustomTextLayout.cpp#L414 <!-- A clear and concise description of what you want to happen. --> If no glyphs can be found (which I assume is a rather rare case), then the fallback analysis is necessary.
claunia added the Area-RenderingIssue-TaskProduct-TerminalArea-Performance labels 2026-01-31 04:19:02 +00:00
claunia commented 2026-01-31 04:19:03 +00:00
Author
Owner
Copy Link

@skyline75489 commented on GitHub (Aug 3, 2021):

/cc @miniksa

@skyline75489 commented on GitHub (Aug 3, 2021): /cc @miniksa
claunia commented 2026-01-31 04:19:04 +00:00
Author
Owner
Copy Link

@zadjii-msft commented on GitHub (Aug 3, 2021):

That makes sense to me

@zadjii-msft commented on GitHub (Aug 3, 2021): That makes sense to me
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
⛺ Reserved
A11yCO
A11yMAS
A11ySev1
A11ySev2
A11ySev3
A11yTTValidated
A11yUsable
A11yVoiceAccess
A11yWCAG
Area-Accessibility
Area-AtlasEngine
Area-AzureShell
Area-Build
Area-Build
Area-Chat
Area-CmdPal
Area-CodeHealth
Area-Commandline
Area-CookedRead
Area-DefApp
Area-Extensibility
Area-Fonts
Area-GroupPolicy
Area-i18n
Area-Input
Area-Interaction
Area-Interop
Area-Localization
Area-Output
Area-Performance
Area-Portable
Area-Quality
Area-Remoting
Area-Rendering
Area-Schema
Area-Server
Area-Settings
Area-SettingsUI
Area-ShellExtension
Area-ShellExtension
Area-ShellExtension
Area-Suggestions
Area-Suggestions
Area-TerminalConnection
Area-TerminalControl
Area-Theming
Area-UserInterface
Area-VT
Area-Windowing
Area-WPFControl
AutoMerge
Blocking-Ingestion
Culprit-Centennial
Culprit-WinUI
Disability-All
Disability-Blind
Disability-LowVision
Disability-Mobility
External-Blocked-WinUI3
Fixed
Gathering-Data
good first issue
HCL-E+D
HCL-WindowsTerminal
Help Wanted
Impact-Compatibility
Impact-Compliance
Impact-Correctness
Impact-Visual
In-PR
InclusionBacklog
InclusionBacklog-Windows TerminalWin32
InclusionCommitted-202206
Issue-Bug
Issue-Docs
Issue-Feature
Issue-Feature
Issue-Question
Issue-Samples
Issue-Scenario
Issue-Task
Needs-Attention
Needs-Author-Feedback
Needs-Bisect
Needs-Discussion
Needs-Repro
Needs-Tag-Fix
Needs-Tag-Fix
Needs-Triage
No-Recent-Activity
Priority-0
Priority-1
Priority-2
Priority-3
Product-Cmd.exe
Product-Colortool
Product-Colortool
Product-Colortool
Product-Conhost
Product-Conpty
Product-Meta
Product-Powershell
Product-Terminal
Product-WSL
pull-request
Mirrored from GitHub Pull Request
 Resolution-Answered
Resolution-By-Design
Resolution-Duplicate
Resolution-External
Resolution-Fix-Available
Resolution-Fix-Committed
Resolution-No-Repro
Resolution-Won't-Fix
Severity-Blocking
Severity-Crash
Severity-DataLoss
spam
this-will-be-a-breaking-change
Tracking-External
WindowsTerminal_Win32
Work-Item
zAskModeBug
zInbox-Bug
No Label Area-Performance Area-Rendering Issue-Task Product-Terminal
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
claunia
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: starred/terminal#14769
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?