[GitHub] [echarts] pissang commented on issue #15832: Render custom bar plot with log scale

[GitBox <gi...@apache.org>]

pissang commented on issue #15832:
URL: https://github.com/apache/echarts/issues/15832#issuecomment-939710508


   @nhhaidee Hi, `api.size` is not usable in the non-linear axis like `log`. The description of `api.size` can be checked at https://echarts.apache.org/en/option.html#series-custom.renderItem.arguments.api.size. 
   
   The underlying logic of `api.size` is quite simple:
   ```ts
   const p0 = api.coord([arbitraryX, arbitrary]);
   const p1 = api.coord([arbitraryX + size[0], arbitrary + size[1]])
   return [p1[0] - p0[0], p1[1] - p0[1]];
   ```
   
   So it's more like a utility method that assumes the axis is linear. For the non-linear axis, the returned size will depends on the picked `[arbitraryX, arbitrary]`. So this method becomes meaningless in this case.
   
   To fix this issue, ss you can see, you can always use `api.coord` to calculate the size of rectangle:
   
   ```ts
   var start = api.coord([api.value(0), api.value(2)]);
   var end = api.coord([api.value(1), 1]); 
   return {
             type: "rect",
             shape: {
               x: start[0],
               y: start[1],
               width: end[0] - start[0],
               height: end[1] - start[1]
             },
             style: api.style()
           };
   ```
   
   We will improve the doc to explain this point.


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