D14783: [scenes/opengl] Correctly draw shadows when corner tiles are missing

davidedmundson added inline comments.

INLINE COMMENTS

> scene_opengl.cpp:2140
> +{
> +    if (leftRect.right() >= rightRect.left()) {
> +        const qreal halfOverlap = qAbs(leftRect.right() - rightRect.left()) / 2;

just > ?

if they're == then we don't need to do anything

also the qAbs is not needed, we know leftRect.right > rightRect.left

> scene_opengl.cpp:2185
>  
>      const int width = std::max({topLeft.width(), left.width(), bottomLeft.width()})
>                      + std::max(top.width(), bottom.width())

may as well

max(top,bottom) + shadowMargins.left + shadowMargins.right

> scene_opengl.cpp:2246
>      // tile won't be rendered.
> -    bool drawTop = true;
> -    if (topLeftRect.right() >= topRightRect.left()) {
> -        const float halfOverlap = qAbs(topLeftRect.right() - topRightRect.left()) / 2;
> -        topLeftRect.setRight(topLeftRect.right() - halfOverlap);
> -        topRightRect.setLeft(topRightRect.left() + halfOverlap);
> -        drawTop = false;
> -    }
> -
> -    bool drawRight = true;
> -    if (topRightRect.bottom() >= bottomRightRect.top()) {
> -        const float halfOverlap = qAbs(topRightRect.bottom() - bottomRightRect.top()) / 2;
> -        topRightRect.setBottom(topRightRect.bottom() - halfOverlap);
> -        bottomRightRect.setTop(bottomRightRect.top() + halfOverlap);
> -        drawRight = false;
> -    }
> -
> -    bool drawBottom = true;
> -    if (bottomLeftRect.right() >= bottomRightRect.left()) {
> -        const float halfOverlap = qAbs(bottomLeftRect.right() - bottomRightRect.left()) / 2;
> -        bottomLeftRect.setRight(bottomLeftRect.right() - halfOverlap);
> -        bottomRightRect.setLeft(bottomRightRect.left() + halfOverlap);
> -        drawBottom = false;
> -    }
> -
> -    bool drawLeft = true;
> -    if (topLeftRect.bottom() >= bottomLeftRect.top()) {
> -        const float halfOverlap = qAbs(topLeftRect.bottom() - bottomLeftRect.top()) / 2;
> -        topLeftRect.setBottom(topLeftRect.bottom() - halfOverlap);
> -        bottomLeftRect.setTop(bottomLeftRect.top() + halfOverlap);
> -        drawLeft = false;
> -    }
> +    distributeHorizontally(topLeftRect, topRightRect);
> +    distributeHorizontally(bottomLeftRect, bottomRightRect);

There's an interesting hypothetical here.

We're treating the null corners as rectangles at a single point, potentially if you had a large enough topleft shadow no topright corner you'll end up distributing it; and now our null image will get a valid rectangle.

> scene_opengl.cpp:2337
>          ty1 = 0.0;
> -        tx2 = 1.0 - topRight.width() / width;
> +        tx2 = tx1 + top.width() / width;
>          ty2 = topRect.height() / height;

Why this change? We've redistributed topRight so using it should be fine?

REPOSITORY
  R108 KWin

REVISION DETAIL
  https://phabricator.kde.org/D14783

To: zzag, #kwin
Cc: abetts, davidedmundson, kwin, mkulinski, ragreen, jackyalcine, Pitel, iodelay, bwowk, ZrenBot, lesliezhai, ali-mohamed, hardening, jensreuterberg, sebas, apol, mart