Summary
The problem of calculating mouse position in a rotated and scaled DIV is a complex one, involving DOMMatrix and coordinate transformations. To solve this, we need to understand how to apply transformations to the mouse coordinates.
Root Cause
The root cause of this issue is the nested transformation of the DIV elements, which affects the coordinate system. The causes include:
- Scaling: The outer DIV is scaled, which changes the coordinate ratios.
- Rotation: The inner DIVs are rotated, which changes the coordinate axes.
- Nested transformations: The rotations are nested, making it harder to calculate the final coordinates.
Why This Happens in Real Systems
This issue occurs in real systems when:
- Complex layouts are used, involving nested transformations.
- Dynamic content is added, which can change the coordinate system.
- User interactions involve mouse movements, which need to be accurately tracked.
Real-World Impact
The impact of this issue includes:
- Inaccurate mouse tracking, leading to poor user experience.
- Difficulty in implementing drag-and-drop or hover effects.
- Increased development time, as developers struggle to debug and fix the issue.
Example or Code
const target = document.getElementById('target');
target.addEventListener('pointermove', evt => {
const rect = target.getBoundingClientRect();
const x = evt.clientX - rect.left;
const y = evt.clientY - rect.top;
const divX = x / rect.width * target.offsetWidth;
const divY = y / rect.height * target.offsetHeight;
console.log(divX, divY);
});How Senior Engineers Fix It
Senior engineers fix this issue by:
- Understanding the transformation matrix, using DOMMatrix or CSSMatrix.
- Applying inverse transformations, to cancel out the effects of scaling and rotation.
- Using relative coordinates, to account for the nested transformations.
Why Juniors Miss It
Juniors may miss this issue due to:
- Lack of understanding of coordinate transformations and DOMMatrix.
- Insufficient experience with complex layouts and nested transformations.
- Overlooking the impact of scaling and rotation on mouse coordinates.