[Interest] Routing all QML file requests through a custom resource provider

[Max Savenkov]

Hi Dmitry,

As a understand it, qrc is just an index file. I still need to provide
binary data it refers to somehow. Basically, what I don't understand is
this passage in documentation: "a binary resource can be created and at a
later point in application code registered with the resource system.".
Looking at header file, I can see two ways to register a rcc file. This
first is by specifying filename to QResource::registerResource. That one
won't work, since Qt will try to load this file from conventional
filesystem, while it is really located in my resource provider (basically,
in memory).

There is a second overload of registerResource, which takes a pointer to
rccData. Which LOOKS like that I need, but it suspiciously missing "size"
argument, so I'm not really sure what this call does. Unless, of course, it
just registers a pointer to memory as a resource and just assumes it's a
correctly formatted output of rcc that at least contains some header with
size? In which case I certainly can use it, and it will solve my problems,
but then it seems unsafe to me.


2016-06-17 12:45 GMT+03:00 Dmitry Volosnykh <dmitry.volosnykh at gmail.com>:

> Hi, Max!
>
> To be honest, I did not understand in all the details what you are trying
> to achieve. Anyway that looks way complex indeed.
>
> Since you are inclined to pack all you resources into auxiliary file like
> zip package, you are surely okay with static content. Having this said, you
> should be fine using conventional .qrc files (this is what you named Qt
> resource system). These files are easily accessed (i.e. viewed, edited,
> etc.) from Qt Creator. Qt Designer tools understand them perfectly fine, as
> well. Also, there should be no issues when importing QML components from
> your .qml files once you feed QML engine with root .qml file stored inside
> .qrc file.
>
> Regards,
> Dmitry.
>
> On Fri, Jun 17, 2016 at 12:09 PM Max Savenkov <max.savenkov at gmail.com>
> wrote:
>
>> Hello,
>>
>> Once again, I'm trying to use Qt (in this case, QtQuick/QML) for game
>> development. The game is going to store all its resources in a package
>> (it might be zip, or a custom format) when deployed, but during
>> development, resources are available in the usual filesystem. This
>> difference is hidden by game's resource provider, which maps resource
>> name to a file or an entry in package.
>>
>> This works for the game itself, but how can I make QML load images,
>> imports and other resources from game's resource provider? (also, I'd
>> like to view my QML files in Designer, which means I can't use custom
>> image providers in QML code itself)
>>
>> I see two possibilities, but I'm not sure of either one.
>>
>> 1) Use dynamic resources produced by rcc. When loading a QML file from
>> C++, also load relevant rcc data (from game's resources) and register it
>> with Qt resource system to make it accessible. This sounds workable, but
>> I'm not sure how exactly to make it happen. Suppose I got a binary
>> buffer from game's resources. How do I register it in Qt?
>>
>> 2) Use a system of crutches.
>> * Register Url Interceptor with my QMLEngine, such that:
>>      - any URL that contains an image is changed into
>> "image:/my_resource_provider/imagename.png"
>>      - any URL that contains qml or qmldir is change into... What? There
>> is no way to register a special loader for QML imports. But I guess I
>> can change it into a network request, by substituting shcema to, for
>> example, "my_provider"
>> * Register image provider with name "my_resource_provider" that loads
>> images from my resource system.
>> * Register a custom network access manager factory/manager/network reply
>> that load QML files from my system instead of network. This doesn't
>> quite work, however, because QML at some point for whatever reason
>> checks that URL used to load qml file is local...
>>
>> So, I'm stumped. This should be WAY easier... And it was, before
>> AbstractFileEngine was made private. But I really don't want to use
>> private APIs if I can avoid it.
>> An argument against AbstractFileEngine was made, that virtual FS should
>> be implemented "at OS level" - but I simply cannot see how a game can
>> implement it at OS level, because it's a game 0_o.
>> _______________________________________________
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>> Interest at qt-project.org
>> http://lists.qt-project.org/mailman/listinfo/interest
>>
>
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