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

[Jose Pereda]

On Fri, 3 Sep 2021 21:19:09 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Jose Pereda has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Use color to int32 converter instead of hash
>
> 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;
}

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

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