Markdown "Show Source" should go to previous tab if open

[miguelsolorio]

Issue Type: Bug

When using the Markdown preview, the "Show Source" action should be smart enough to know that the source is open and go to that tab. Same applies to the preview tab, if there is already a preview tab open switch focus there. Otherwise you're in this endless loop of creating duplicate tabs.

VS Code version: Code - Insiders 1.35.0-insider (a5536b8, 2019-05-20T05:15:57.974Z)
OS version: Darwin x64 18.2.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-7920HQ CPU @ 3.10GHz (8 x 3100)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: enabled rasterization: enabled surface_synchronization: enabled_on video_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	3, 3, 3
Memory (System)	16.00GB (0.67GB free)
Process Argv
Screen Reader	no
VM	0%

Extensions (30)

Extension	Author (truncated)	Version
vscode-browser-preview	auc	0.5.4
vscode-opennewinstance	chr	0.0.6
bracket-pair-colorizer	Coe	1.0.61
vscode-svgviewer	css	2.0.0
vscode-eslint	dba	1.9.0
gitlens	eam	9.7.4
vsc-material-theme	Equ	2.8.2
prettier-vscode	esb	1.9.0
azure-virtual-machine-explorer	for	0.0.2
vscode-pull-request-github-insiders	Git	1.137.0
vscode-colorize	kam	0.8.10
theme-monokai-pro-vscode	mon	1.1.13
vscode-azureappservice	ms-	0.14.0
python	ms-	2019.4.12954
remote-containers	ms-	0.53.0
remote-ssh	ms-	0.37.0
remote-ssh-edit	ms-	0.37.0
remote-ssh-explorer	ms-	0.37.0
remote-wsl	ms-	0.36.0
azure-account	ms-	0.8.4
azurecli	ms-	0.4.5
vscode-typescript-tslint-plugin	ms-	1.0.0
debugger-for-chrome	msj	4.11.3
vetur	oct	0.21.0
vscode-docker	Pet	0.6.2
vscode-yaml	red	0.4.0
code-settings-sync	Sha	3.2.9
ayu	tea	0.18.0
WebTemplateStudio-dev-nightly	WAS	0.0.1914003
markdown-all-in-one	yzh	2.3.1

(17 theme extensions excluded)

[chirag64]

I'd like to give this a try

[chirag64]

Ok, I could use some help on this issue. I traced the click call to the function openTextDocument in extHost.api.impl.ts, but am not sure if I should be making any changes here since it will very likely affect other functionalities as well.

I also noticed that if I have the file already open in the same split window pane, it will open that instead of creating a new split pane, but it is calling the same code with the same parameters here even when it opens a new pane with a new tab. So I am confused how calling the same function with the same parameter exhibits different behaviors (opening a new pane with a new tab vs opening an already open tab in the same pane).

Some pointers around this would be very helpful, thanks

[chirag64]

@mjbvz sorry for tagging you, not sure if you got a chance to see my previous comment. Can you please help out?

[mjbvz]

@chirag64 The api you linked to is a good starting point but that is part of core VS Code. You want the caller of that api, which in the case is the markdown extension.

How I think this feature should work:

1. In the markdown extension, we maintain a list of active previews. These should track which column created the preview. This is likely already passed in with PreviewSettings, we just don't store the resourceColumn anywhere as far as I remember.
2. When the show source command is invoked, use the preview's column information to decide which column to show the preview in