Suggestion: Renderers need to know where they're drawing

General JUCE discussion
1

As we discussed in this topic: http://www.juce.com/forum/topic/text-rendering-suggestion-need-jules-eyes

Subpixel rendering needs to know the pixel orientation of the monitor it is rendering to. I've got all other code set up for this, so that i know what monitors is what configuration etc., only thing is: LowLevelSoftwareRenderers don't know where they are drawing, beyond an offset to an arbitrary image. This means it cannot identify what pixel setting it should use, account for screen rotations/resolutions and so on.

Also, another thing that would be nice is, if the renderer knows whether it is rendering to a screen context or an image (similarly to isVectorDevice()).

Jules, how do you propose one solves this problem? 

One solution, without breaking anything, would be to add something like:

virtual juce::LowLevelGraphicsContext * LookAndFeel::createGraphicsContextAdvanced(
    const Image & buffer, const Point<int> origin, const RectangleList<int> clip, bool isScreenContext, const Point<int> componentPosition)
{
    // default implementation just forwards:
    return createGraphicsContext(buffer, origin, clip);
}

Such that you can override this if you can use the additional information. All the normal places that would create a graphics context (like paint handlers) would now call this instead. I realize that this is really crippling the abstraction, but if you want to optimize rendering per-display you'll need something like this sooner or later.. 

Edit: 

Also, another thing: Would it be possible to listen to system notifications related to screen resolution/resizing etc? Currently, they get dumped into Desktop::Displays::refresh(). If Displays could have a listener interface, that would be sweet.

 

Regards

2

Hi Mayae, unfortunately I can't help with you're problem specifically, but would you care to share how you are checking the monitor information? I need to find out if the monitor my GUI is being shown on is retina or not :)

3

The code is still WIP on osx. You can find some examples in the zip i posted in the op of this topic: http://www.juce.com/forum/topic/text-rendering-suggestion-need-jules-eyes

 

For checking if a screen is retina-like, I suppose something like this would work:

bool isScreenScaled = juce::Desktop::getInstance().getDisplays().getDisplayContaining(<WHERE YOU WANT TO RENDER>).scale != 1;

If you need to get in-depth information about monitors on OSX, you will need to iterate [NSSCreen screens] and get a dictionary out of them. For specific components, I'm pretty sure you can just use Component::getDesktopScaleFactor()?

 

However, you cannot do this yet unless jules implements the change i suggested in the OP - because renderers do not know their position on the screen. Unless - if you're doing this inside your paint() or similar method, then just use topLeftPosition of the last parent of your component!

4

Yes, sounds like these would need to become properties of the low level context object - adding a virtual method to ask whether it has a sub-pixel ordering or not would be the thing to do.