当 WebGL 渲染器将单元宽度设为最大值时,IME 预编辑不会与单元网格对齐

The composition view is positioned and sized from the renderer's cell dimensions, but the text inside it is laid out by normal DOM text layout. The WebGL renderer floors the cell width to whole device pixels while the DOM renderer does not, so on a `devicePixelRatio: 1` display the two disagree and the preedit drifts away from the grid by one cell fraction per character.