Hey everyone I am drawing some rectangles in canvas and scal kotlinlang #compose

on canvas instead of my original approach and that does not seem to render anything (or render too small for it to be visible) so I was wondering if that is the correct approach or not? Code in thread

private fun Screen(displayMatrix: DisplayMatrix, modifier: Modifier = Modifier, scale: Int = Display.SCALE) {
    Canvas(modifier.scale(scale.toFloat())) {
      for (y in 0 until Display.ROWS) {
        for (x in 0 until Display.COLUMNS) {
          val color = if (displayMatrix.getPixel(x, y)) Color.White else Color.Black
          drawRect(
            color = color,
            topLeft = Offset((x).toFloat(), (y).toFloat()),
            size = Size(1.toFloat(), 1.toFloat())
          )
        }
      }
    }
  }

Original code

private fun Screen(displayMatrix: DisplayMatrix, modifier: Modifier = Modifier, scale: Int = Display.SCALE) {
    Canvas(modifier) {
      for (y in 0 until Display.ROWS) {
        for (x in 0 until Display.COLUMNS) {
          val color = if (displayMatrix.getPixel(x, y)) Color.White else Color.Black
          drawRect(
            color = color,
            topLeft = Offset((x * scale).toFloat(), (y * scale).toFloat()),
            size = Size(scale.toFloat(), scale.toFloat())
          )
        }
      }
    }
  }

Dan MacNeil

01/21/2022, 2:04 PM

In your first code block you are setting the size of the rectangle to 1x1 pixels. In your second code block you are using the scale for the rectangle size.

Aditya Wasan

01/22/2022, 10:45 AM

Yeah, but I’m also calling

Modifier.scale

on the parent canvas 🤔

Dan MacNeil

01/22/2022, 2:48 PM

The original code block is scaling/offseting from the upper left corner. The second code block will be scaling from the center of the canvas which is the default pivot point. That may be pushing your graphics off the screen. Modifier.graphicsLayer should let you change the pivot point, I think. I'm just learning this stuff myself.🙂

Aditya Wasan

01/24/2022, 4:51 AM

I didn’t think about that. I’ll definitely take a look. Thanks for helping :)

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