Set windows size of QuickLook Plugin

cocoa, objective-c, quicklook

Solution

Thought I'd dig a little on this. I have not tried any of the following suggestions, so nobody get their hopes up. I'll assume you're using the generator callback:

OSStatus (*GeneratePreviewForURL)(
    void *thisInterface,
    QLPreviewRequestRef preview,
    CFURLRef url,
    CFStringRef contentTypeUTI,
    CFDictionaryRef options
);

Before anything else, you might manually check the `options` dictionary argument and verify that the `kQLPreviewPropertyWidthKey` and `kQLPreviewPropertyHeightKey` keys are indeed mapped to the desired `CFNumber` values.

Referring to each of these properties, the Apple QuickLook programming guide says:

Note that this property is a hint; Quick Look might set the width automatically for some types of previews. The value must be encapsulated in a CFNumber object.

(Edit: If your preview representation is flexible, you might try finding a preview type for which QuickLook honors your size hints, as per the statement above. Just a thought.)

Running `nm` on the QuickLook framework binary revealed some undocumented `kQLPreviewProperty--` constants as well as the aforementioned width and height keys. One that caught my attention was `kQLPreviewPropertyAutoSizeKey`. Recalling Apple's statement about ignoring the hints to set the size automatically, this might be significant? Following the convention in `QuickLook.framework/Headers/QLBase.h`, you might try declaring

extern const CFStringRef kQLPreviewPropertyAutoSizeKey;

Then you could try associating a CFNumber 0 with that property key in the `options` dictionary. There are other undocumented keys of note, such as `kQLPreviewPropertyAttributesKey`.

Back to the Info.plist you mentioned, Apple says about those keys `QLPreviewWidth` and `QLPreviewHeight`:

This number gives Quick Look a hint for the width (in points) of previews. It uses these values if the generator takes too long to produce the preview. (emphasis added)

This is where someone makes the terrible suggestion of calling sleep() in your generator. But I'm perplexed as to why Apple would make following the size hints dependent on the generator latency. (?)

Edit: Also note the above statement says the Info.plist hints must be expressed in points (not pixels), a unit dependent on the user's screen resolution.

Problem

I'm building a QuickLook plugin. I want to change the width of the windows that pops up when user hits the spacebar. I've read there are two keys in the info.plist file of the project where height and width are customisable. Even if I change those values I can't get the size of the preview windows to my desired one. I don't know what else to try. Any idea? Thanks!

Original source