RFR: 8238954: Improve performance of tiled snapshot rendering [v14]

[Ambarish Rapte]

On Tue, 30 Jun 2020 09:44:33 GMT, Frederic Thevenet <github.com+7450507+fthevenet at openjdk.org> wrote:

>> Issue JDK-8088198, where an exception would be thrown when trying to capture a snapshot whose final dimensions would be
>> larger than the running platform's maximum supported texture size, was addressed in openjfx14. The fix, based around
>> the idea of capturing as many tiles of the maximum possible size and re-compositing the final snapshot out of these, is
>> currently only attempted after the original, non-tiled, strategy has already failed. This was decided to avoid any risk
>> of regressions, either in terms of performances and correctness, while still offering some relief to the original
>> issue.  This follow-on issue aims to propose a fix to the original issue, that is able to correctly decide on the best
>> snapshot strategy (tiled or not) to adopt before applying it and ensure best performances possible when tiling is
>> necessary while still introducing no regressions compared to the original solution.
>
> Frederic Thevenet has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Prevent attempt to render tiles with a 0 sized dimension.

The code looks good to me too, suggested minor change.

modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/QuantumToolkit.java line 1638:

> 1637:                         renderWholeImage(x, y, w, h, rf, pImage);
> 1638:                     }
> 1639:                     params.platformImage = pImage;

I tried to write this code using for loop to make it little easy for reader to understand. This is just a suggestion, I
leave it to you to whether replace it or not,

	int mTileWidth = computeTileSize(w, maxTextureSize);
	int mTileHeight = computeTileSize(h, maxTextureSize);
	IntBuffer buffer = IntBuffer.allocate(mTileWidth * mTileHeight);

	int mTileXOffset = 0;
	int mTileYOffset = 0;
	for (mTileXOffset = 0; (mTileXOffset + mTileWidth) <= w; mTileXOffset += mTileWidth) {
		for (mTileYOffset = 0; (mTileYOffset + mTileHeight) <= h; mTileYOffset += mTileHeight) {
			renderTile(x, mTileXOffset, y, mTileYOffset, mTileWidth, mTileHeight,
					buffer, rf, tileRttCache, pImage);
		}
	}

	int rTileXOffset = mTileXOffset;
	int rTileWidth = w - rTileXOffset;
	if (rTileWidth > 0) {
		for (int rTileYOffset = 0; (rTileYOffset + mTileHeight) <= h; rTileYOffset += mTileHeight) {
			renderTile(x, rTileXOffset, y, rTileYOffset, rTileWidth, mTileHeight,
					buffer, rf, tileRttCache, pImage);
		}
	}

	int bTileYOffset = mTileYOffset;
	int bTileHeight = h - bTileYOffset;
	if (bTileHeight > 0) {
		for (int bTileXOffset = 0; (bTileXOffset + mTileWidth) <= w; bTileXOffset += mTileWidth) {
			renderTile(x, bTileXOffset, y, bTileYOffset, mTileWidth, bTileHeight,
					buffer, rf, tileRttCache, pImage);
		}
	}

	if (rTileWidth > 0 &&  bTileHeight > 0) {
		renderTile(x, rTileXOffset, y, bTileYOffset, rTileWidth, bTileHeight,
				buffer, rf, tileRttCache, pImage);
	}

modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/QuantumToolkit.java line 1564:

> 1563:                     if (h > maxTextureSize || w > maxTextureSize) {
> 1564:                         // The requested size for the screenshot is too big to fit a single texture,
> 1565:                         // so we need to take several snapshot tiles and merge them into pImage

Very minor: screenshot should be changed to snapshot.

modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/QuantumToolkit.java line 1635:

> 1634:                     else {
> 1635:                         // The requested size for the screenshot fits max texture size,
> 1636:                         // so we can directly render it in the target image.

Very minor: screenshot should be changed to snapshot.

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PR: https://git.openjdk.java.net/jfx/pull/112