Editor decoration doesn't show up when changing from multiple lines to one line at the same time

[roblourens]

I set a 'placeholder' editor decoration here:

vscode/src/vs/workbench/contrib/chat/browser/contrib/chatInputEditorContrib.ts

Line 146 in 7cfb875

this.widget.inputEditor.setDecorationsByType(decorationDescription, placeholderDecorationType, decoration);

I noticed that when the chat input had multiple lines of text in it, then the placeholder doesn't show up. Here I show it not working, then working with a single line of text.

Maybe it's related somehow to the issue we had in #203902? I can't debug this on my own, but it reproes 100% of the time for me, happy to help investigate.

[hediet]

setTimeout(() => {
  this.widget.inputEditor.setDecorationsByType(decorationDescription, placeholderDecorationType, decoration);
}, 0);

This fixes it, but it sucks.

@alexdima it looks like setDecorationsByType cannot be used when certain events are fired.
Looks like the view fires a scroll change event, which causes the event queue to flush, which causes a content change event, which calls the callback that sets the decoration...

[alexdima]

AFAIK nothing changed here in the editor recently, so @roblourens not sure if this is bad enough to add the workaround Henning found for this release on your side.

IMHO we need to add proper placeholder API to the editor instead of doing this from the outside with injected text. We now have something like 3 or 4 places implementing placeholder text via injected text, which doesn't make sense to me.

[hediet]

Created #208976 for the placeholder API.
Feel free to close this one in favor of #208976

[hediet]

The event stack is quite complicated. Below is the stack of where the decoration is set.
The core problem is that ViewLines.renderText fires an event and allows event handlers to run immediately:

Error
at eval
at vs/workbench/contrib/chat/browser/contrib/chatInputEditorContrib.ts:147:8
at vs/workbench/contrib/chat/browser/contrib/chatInputEditorContrib.ts:68:76
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1167:8
at vs/base/common/event.ts:1178:8
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1631:29
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/editor/common/viewModelEventDispatcher.ts:64:17
at vs/editor/common/viewModelEventDispatcher.ts:39:7
at vs/editor/common/viewModel/viewModelImpl.ts:135:25
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/editor/common/viewLayout/viewLayout.ts:127:32
at vs/editor/common/viewLayout/viewLayout.ts:350:19
at vs/editor/common/viewLayout/viewLayout.ts:340:7
at vs/editor/browser/viewParts/lines/viewLines.ts:676:38
at vs/editor/browser/viewParts/lines/viewLines.ts:560:7
at vs/editor/browser/viewParts/lines/viewLines.ts:513:14
at vs/editor/browser/viewParts/lines/viewLines.ts:643:12
at vs/editor/browser/view.ts:501:21
at func vs/editor/browser/view.ts:676:9
at safeInvokeNoArg vs/editor/browser/view.ts:447:15
at vs/editor/browser/view.ts:582:8
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1566:23
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1384:8
at vs/workbench/contrib/chat/browser/chatInputPart.ts:468:21
at vs/workbench/contrib/chat/browser/chatInputPart.ts:450:14
at vs/workbench/contrib/chat/browser/chatWidget.ts:769:17
at vs/workbench/contrib/chat/browser/chatWidget.ts:603:8
at vs/workbench/contrib/chat/browser/chatWidget.ts:576:69
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1167:8
at vs/base/common/event.ts:1178:8
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1676:37
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/editor/common/viewModelEventDispatcher.ts:64:17
at vs/editor/common/viewModelEventDispatcher.ts:109:7
at vs/editor/common/viewModel/viewModelImpl.ts:147:26
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/editor/browser/config/editorConfiguration.ts:105:24
at vs/editor/browser/config/editorConfiguration.ts:90:64
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/editor/browser/config/elementSizeObserver.ts:117:22
at vs/editor/browser/config/elementSizeObserver.ts:98:7
at vs/editor/browser/config/editorConfiguration.ts:167:26
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1382:22
at vs/workbench/contrib/chat/browser/chatInputPart.ts:468:21
at vs/workbench/contrib/chat/browser/chatInputPart.ts:450:14
at vs/workbench/contrib/chat/browser/chatWidget.ts:769:17
at vs/workbench/contrib/chat/browser/chatWidget.ts:572:9
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/workbench/contrib/chat/browser/chatInputPart.ts:320:28
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1167:8
at vs/base/common/event.ts:1191:8
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1702:35
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/editor/common/viewModelEventDispatcher.ts:64:17
at vs/editor/common/viewModelEventDispatcher.ts:109:7
at vs/editor/common/viewModel/viewModelImpl.ts:1109:25
at vs/editor/common/viewModel/viewModelImpl.ts:1043:7
at vs/editor/common/viewModel/viewModelImpl.ts:1064:7
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1132:28
at vs/editor/browser/widget/codeEditor/codeEditorWidget.ts:1763:10
at vs/editor/browser/view/viewController.ts:88:23
at vs/editor/browser/controller/textAreaHandler.ts:336:24
at vs/base/common/event.ts:1156:12
at vs/base/common/event.ts:1187:8
at vs/editor/browser/controller/textAreaInput.ts:221:80
at vs/base/common/async.ts:1022:15
at vs/base/common/async.ts:1017:8