Markdown image paste regressions

[wxiaoguang]

Regression of Downscale pasted PNG images based on metadata #29123 :

1. The pasted image is not clickable (unable to view the full image)
2. The URL path doesn't contain sub-path if the Gitea instance is deployed under a sub-path.
   • From discord report: Pasting image from the clipboard the Javascript (Paste.js) embeds the image via html code but the src attribute is set to value: /attachments/<GUID>. Using a configuration in which the Gitea application is served on a subpath of the domain name, for example: https://domain.name/git the image is not rendered.

[wxiaoguang]

@silverwind

[silverwind]

Both issues indicate there is some processing that works on ![]() images, but not on the <img> variant, so it's not a direct regression from that PR because <img> is supported since a long time, it just was never noticed.

[silverwind]

Can confirm above suspicion, there is transformImage which apparently is never applied on user-supplied <img> tags because maybe Goldmark does not emit it as ast.Image or something.

[silverwind]

Yeah so this is no easy fix in backend because <img> tags do not go through goldmark AST processing I think, they likely go through as raw html so need to introduce the wrapper link here:

gitea/modules/markup/html.go

Line 399 in aace3bc

if node.Data == "img" {

[wxiaoguang]

Actually it is a regression. No matter how markdown / img work, as an end users:

1. I would like to click an image to show the full size (especially when it is a full-size screenshot)
2. I would like to deploy Gitea under a sub-path and paste images into the editor

I do not care about <img> or something else, but now:

1. I can't
2. I can't

---

As a developer, I think there is an undefined / unclear behavior for the embedded <img> tag when it has a relative src link. But I do not think it's worth to make it more complex than it should be at the moment.

[wxiaoguang]

-> Make pasted "img" tag has the same behavior as markdown image #31235

[silverwind]

I would like to click an image to show the full size (especially when it is a full-size screenshot)

At least Firefox has the built-in on all images "Open image in new tab" 😉