Which rendering phase does redraw and reflow affect?

Redrawing and reflow will affect the construction and layout stages of the rendering tree: During the web page rendering process, the browser will sequentially build the DOM tree, build the CSSOM tree, and then merge them into a rendering tree, and then perform layout "Reflow" and draw "redraw" operations are finally displayed on the user interface.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

Redraw and reflow affect the construction and layout phases of the render tree. During the web page rendering process, the browser will sequentially build the DOM tree, build the CSSOM tree, and then merge them into a rendering tree, then perform layout (reflow) and drawing (redrawing) operations, and finally display them on the user interface.

The occurrence of redraw and reflow affects the construction and layout phases of the render tree because they both involve the redrawing of calculations and styles of the render tree. Specifically:

1. Reflow will trigger the re-layout of the rendering tree, that is, the browser needs to recalculate the layout information of the element based on the element's size, position and other information, and then update the rendering Tree and page layout.

2. Repaint (Repaint) is after the rendering tree is constructed, when the style of the element changes but does not affect the layout, the browser only needs to redraw the affected part, and No rearrangement is required.

Therefore, redrawing and reflow directly affect the construction and layout stages of the rendering tree, affecting the rendering performance of the entire page. In front-end development, attention needs to be paid to reducing the frequent occurrence of redraws and reflows to improve page rendering performance.

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