RFR: 8090547: Allow for transparent backgrounds in WebView [v6]

[Kevin Rushforth]

On Mon, 6 Sep 2021 09:28:20 GMT, Jose Pereda <jpereda at openjdk.org> wrote:

>> modules/javafx.web/src/main/java/com/sun/webkit/WebPage.java line 97:
>> 
>>> 95: 
>>> 96:     private int fontSmoothingType;
>>> 97:     private Color backgroundColor = Color.WHITE;
>> 
>> This might be a problem, since there are code paths that bypass `setBackgroundColor(Color)`. I might recommend storing the converted 32-bit color, and then checking that for transparency. Either that or you will need to derive a `Color` from a 32-bit int in the cases that set a 32-bit int color directly. The former is probably easier.
>
> In my first commit there was already a method to get the color out of the 32-bit int (which was still referred as hash value at that time):
> 
> private static Color getColorFromHash(int hash) {
>          String hexString = Integer.toHexString(hash);
>          int length = hexString.length();
>          return Color.valueOf("#" + "0".repeat(8 - length) + hexString);
> }
> 
> If we keep it in `WebPage` (renaming it accordingly to `getColorFromInt32` for instance), we could do:
> 
> 
> public void setBackgroundColor(Color backgroundColor) {
>         setBackgroundColor(getColorInt32Value(backgroundColor));
> }
> 
> public void setBackgroundColor(int backgroundColor) {
>            this.backgroundColor = getColorFromInt32(backgroundColor);
>            lockPage();
>     ...
> }
> ```    
> which looks a little bit ugly.
> 
> The other option, as you mention, is finding out if the 32-bit int has alpha 0 or 1, which can be done storing only the int value, not the color, so this looks cleaner, we don't really need to hold a reference to the Color after all:
> 
> 
> private int backgroundColor = -1; // Color.WHITE
> 
> public void setBackgroundColor(Color backgroundColor) {
>         setBackgroundColor(getColorInt32Value(backgroundColor));
> }
> 
> public void setBackgroundColor(int backgroundColor) {
>            this.backgroundColor = backgroundColor;
>            lockPage();
>     ...
> }
> 
> private boolean isBackgroundTransparent() {
>         return (backgroundColor & 0x000000FF) == 0;
> }
> 
> private boolean isBackgroundOpaque() {
>         return (backgroundColor & 0x000000FF) == 255;
> }

Yes, the second approach does look cleaner, although I think the initial `backgroundColor` would be better defined as a hex constant, `0xffffffff` for clarity.

-------------

PR: https://git.openjdk.java.net/jfx/pull/563