fix: issue#16749 colorAlpha check

[jiawulin001]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Fix the problem where itemStyle.colorAlpha does not apply to the view.

Fixed issues

• [Bug] treemap.data.itemStyle.colorAlpha is not work, when color has value. #16749

Details

Before: What was the problem?

The attribute itemStyle.colorAlpha is not working to change the opacity.
A rectangle applying color = 'cyan' and colorAlpha = 0.3 has the same color as one applying only 'color = 'cyan'.

After: How is it fixed in this PR?

A simple check is added to Model.ts to see if colorAlpha comes together with color. However this is adding details into model, which I think is not good.
The result after fix is:

Code to reproduce

option = {
  series: [
    {
      type: 'treemap',
      label: {
        color: 'black',
      },
      data: [
        {
          name: 'nodeA',
          value: 10,
          color: ['red', 'pink'],
          children: [
            {
              name: 'nodeAa',
              value: 4,
              itemStyle: {
                color: 'cyan',
                colorAlpha: 0.3, // not work
              },
            },
            {
              name: 'nodeAb',
              value: 6,
              itemStyle: {
                color: 'cyan', // For Comparison
              },
            },
          ],
        },
        {
          name: 'nodeB',
          value: 20,
          children: [
            {
              name: 'nodeBa',
              value: 20,
              children: [
                {
                  name: 'nodeBa1',
                  value: 20,
                },
              ],
            },
          ],
        },
      ],
    },
  ],
};

Misc

• The API has been changed (apache/echarts-doc#xxx).
• This PR depends on ZRender changes (ecomfe/zrender#xxx).

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[pissang]

It will bring colorAlpha(and colorSaturation) to itemStyle of all series. I think we need further discussion if it's necessary.

First of all these two only do modification on the color property. It's a work that can be easily done by developers by changing the alpha value in rgba / 'hsl' string or using echarts.color.modifyAlpha and echarts.color.modifyHSL utility methods. I can't think of other benefits, or I may have missed something here, remind me if so. We tend to be very conservative in adding this kind of features.

If we do so, we need to do more work to keep the consistent. For example, areaStyle and lineStyle should also provide this ability. And what about borderColor, or even textStyle.color, shadowColor?

[jiawulin001]

@pissang I agree, I think doing reduction is better than addition here. I would prefer removing colorAlpha from itemStyle because user can set opacity easily with rgba at color. Shall I submit another PR to try removing colorAlpha?

[pissang]

@jiawulin001 Sure, we can deprecate it progressively. For example, we can remove it in the doc at first. Then using warning method to tell developers not to use it anymore. Finally we can remove it in the major versions.