Preview pane improvements 2

[winston-de]

to-do

• Folder previews Preview pane for folders #3400
• Shortcut previews
• Move preview pane code-behind to a view model
• Show thumbnails when no preview control/extension exists
• Fix issue where preview pane doesn't show in search results
• Allow attempting to load as text file even if file has no extension
• Reduce text cutoff
• Automatically preview readmes when no file is selected (Automatically preview readme files when no file is selected #3502)
• Add option to open preview pane by default
• Cache file property list from json file to reduce inefficiency
• Improve code quality for adaptive pane
• Enable opening links from markdown and web preview
• Try to fix and re-implement code previews, if not possible remove altogether
• Attempt to add shadow for pane
• Don't try and load hidden items
• Show different message when no item is selected Preview pane should say no item selected when there's no selected item #3446

Closes #3446

Thumbnail preview:

[d2dyno1]

Item tiles with names for folder preview would be perfect!

+ bit smaller icons

[winston-de]

I was able to get the shadow effect working, which was requested in the original PR.
Should I keep it?

[yaira2]

@winston-de Can you try casting the shadow on the preview pane?

[winston-de]

@yaichenbaum From the content pane, right?

[yaira2]

@yaichenbaum From the content pane, right?

Right

[winston-de]

@yaichenbaum

[winston-de]

Also, I'm trying to load the thumbnail for shortcut previews, but currently the function for sending the request to the full trust process is located in ItemViewModel. Would it be alright if I moved it to it's own helper class?

[yaira2]

@winston-de I know it's not directly connected to the preview pane, but what if shadows were added to the navigation and status bar?

[winston-de]

Yes, though right now it doesn't work well at all if the preview pane also has a shadow because the elevations for the preview pane and content would be inconsistent. I'll work on using a drop shadow instead.

For now, here's what the shadows for the nav toolbar and status bar would look.

[yaira2]

@winston-de Once the paddings/margins and margins are sorted out, I think would look pretty good.

[winston-de]

@yaichenbaum I remember you saying something about changing the properties icon so it wasn't the same as the icon for the preview pane. I found one that I think would work, but it doesn't seem to be in the current sheet.

https://github.com/raw/microsoft/fluentui-system-icons/master/assets/Wrench/SVG/ic_fluent_wrench_24_regular.svg

[yaira2]

@yaichenbaum I remember you saying something about changing the properties icon so it wasn't the same as the icon for the preview pane. I found one that I think would work, but it doesn't seem to be in the current sheet.

https://github.com/raw/microsoft/fluentui-system-icons/master/assets/Wrench/SVG/ic_fluent_wrench_24_regular.svg

That looks good.

[winston-de]

I think I'll have to update the fluent ui glyphs font currently in Files to use it though.

[yaira2]

@winston-de That's probably out of scope for this PR, but it would be great if you could make that change.

[winston-de]

Alright, I redid the shadows with DropShadowPanels instead, because they work much better and require a lot less code. However, I'm not certain if the opacity, blur radius, and offset values are the best.

@yaichenbaum Do you have any input?

[yaira2]

@winston-de Can you try copying the values from the sidebar? By the way, you might want to merge the latest from main to see how the shadows will work with the recent changes.

[winston-de]

Here it is with the values from the sidebar shadow and the newest updates.

[yaira2]

@winston-de That looks good, I am looking into using different colors there as well so that should help the shadow stand out a little more.

[yaira2]

Great work! LGTM