New operator: Scale individual UV faces

[TheDuckCow]

The "why didn't I create this 4 years ago" operator we've all been waiting for. The functionality would be similar to having a modal setting of "individual origins" in the 3D view, but for individual faces in the UV editor view. This helps combat non-perfect pixel lineups or materials whose settings make UV edges bleed between pixels of a texture.

This should be implemented as a modal operator, potentially with its own shortcut key (some modification of s).

[TheDuckCow]

Has now been largely implemented, simpluneed to wrap into s mofs operator and determine the best UI location and/or hotkey to trigger scaling.

Demo here: https://twitter.com/theduckcow/status/899513916149157888

Note to implement the modal,will have to rethink how the caching or undoing will work while minimizing overhead or raw duplication of all UV data initial state, though it might be the only way.

[TheDuckCow]

Note to self: realizing it's a significant effort to implement as a natural modal operator. On top of having the basic function working, it also needs to implement (to make consistent with blender):

• Interpreting the scale factor to apply from mouse position
  • Initial mouse position always sets scale to be equal to 1, and thus the raw distance between initial curser location and the original medium center of selected faces defines the distance of a factor 1, no mater where the actual curser is located
  • As curser moves, scale is set based on [current dist to original center]/[original distance to original center]
  • Negative values are interpreted if the curser crosses the 180º line centered around the original center
• Drawing openGL UI elements
  • Draw a dotted line from current cursor to the origin of the original medium center of the selected faces
  • Draw an inward/outward arrow underneath the current curser location which aligns with the direction of the dotted line
• Interpreting keyboard numeric inputs
  • All keys create individual trigger events, so we need to interpret and delineate between used inputs; e.g. zero versus NUMPAD_0 result in keyboard input of 0
  • Example set of order of entry, space-separated inputs x 0 . 5 and x / 2 and 2 / x all result in the same result: all selected UV's are scaled by 0.5 or a half, constrained along the x axis. Note that for example x 0 . 5 x would the be same as entering 0 . 5 as the double x's essentially cancel out. Likewise, typing / once indicates to invert the number provided, and pressing / again indicates to undue this effect.
  • How to handle the use of "shift"? That may be an acknowledged, not implemented factor as that also affects the logic of how deltas are applied at each level.
• Drawing current value/effect into the window header/footer panel
  • Not currently sure how to do this, need to look up more references
  • Should also show keyboard inputs from user

Goals:

• Implement the dotted line
• Implement the behavior of switching negative/positive value based on crossing the 180 line
• Implement behavior of basic keyboard inputs, e.g. positive/negative toggles by typing -, value inputs like 0.5, and inverting via /, but no interpretation of shift or single-axis scaling

While workarounds exist to implement scaling using built in method and capabilities (e.g. via splitting vertices, scaling in UV editor, and then removing duplicates), that introduces changes of original geometry and is overall a destructive workflow. This method will be direct data manipulations of the UV maps only.

[TheDuckCow]

Reverted on the plans and ambitions above in favor of an "MVP". Using the redo last slider, may revisit making this a modal operator sometime in the future for personal educational purposes. Basic version without modal is currently in dev and will release in 3.1.1.