Simulator: Extend “Send Bitmap” to send screenshot to device

SDK Feature Requests
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The Send Bitmap function in the simulator is very convenient for quickly testing what something looks like on the real device display. Even more convenient would be if there was a variant of it that would send a screenshot of the simulator to the device with one click, without having to save it as a file first. If that functionality already exists, I haven’t found it yet (Simulator 1.13.2 on macOS).

Or, even better, a way to continuously stream the simulator screen to the device display, kind of the opposite of what the Mirror application does.

2 Likes
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Hey @CWalther , not sure if you're still interested in a solution, but I built exactly the tool you were describing: Playdate AntiMirror continuously streams any content from your desktop to your Playdate in real-time via USB. Fun twist: I was able to implement it as web app!

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Very cool, thanks!

It seems a bit fiddly to use with the Simulator though, for two reasons:

  • It’s hard to get a pixel-perfect view of the simulator screen. I haven’t managed yet (with Chromium on macOS) when running the simulator at 1× display scale. When I capture a single window, I haven’t figured out yet what units W and H are. It seems to be neither framebuffer pixels (800×480) nor logical pixels (400×240), but something in between. Maybe Chromium applies some scaling before the data reaches your code. When I capture the whole screen, the dimensions seem to be alright when I choose 400×240, but still some pixels get the wrong color when using “Threshold”, with black areas bleeding into where white should be. I wonder if there is any undue interpolation going on. The only way that works is using “2x Display” in the Simulator, capturing the whole screen, and setting W = 800, H = 480.
  • The web app needs to be connected while the Simulator is not running yet, otherwise the Simulator occupies the serial port.
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Thank you for the feedback!

I am not sure there’s much I can do about the order at which the browser and simulator have to access the USB device. But I have ideas how to make this more accessible via in-app documentation.

As far as the “bleeding” is concerned, I suspect that this is a result of macOS “retina displays”. It occurs to me that I only ever used the screen capture on my external screens with 1:1 pixel ratio. I might be able to reproduce it myself, but if you can: I’d greatly appreciate a screenshot of your simulator window to test against, @CWalther