How to efficiently use the face texture uv editor?

[unhappy_ants]

I'm new to Trenchbroom, and I've watched a few videos on the editor, but I still have some questions about how the red and yellow gizmo works and how the red guidelines work. I'm only working with custom textures; mapping for a non-quake-engine game. First, here's a really crappy texture I'm working with.

About all that I understand is that the white rectangle is the selected face, and that I can rotate the UV plane with the yellow gizmo.

My specific questions are

• What does moving the center of the yellow gizmo do?
• How does the yellow gizmo differ from the red and green axes? What do their two positions mean in relation to each other?
• What's the easiest way to snap the texture to the face boundaries? For example, if I use the mouse to scale in the X I can easily make it snap it to one side of the face, but then if I drag from the other side of the texture then the side I just lined up is no longer lined up.
• Is there any way to make the face outline something that stands out better? For this map I have a lot of textures that cover a wide range of light and dark colors, so I need something easier to see than just a white outline. Is there a way to make it display with a marching ants style (like a selection in gimp, etc.), or something else that stands out?
• Any other videos to help with efficiently editing with the face inspector tool?

 

[h4724]

The red and green axes just show which direction is which in world space. The yellow gizmo is used as the center of rotation, as well as a fixed point for stretching. When rotating, scaling, and translating, the texture-space grid lines and the edges of the face will snap to one another. I'd recommend using arrow keys as much as possible, they'll move the texture by the (world) grid size, and are precise by default, whereas using the mouse in the UV editor requires extra work to get that precision.

When scaling with the mouse, you need to move the yellow gizmo to one edge of your texture, move the texture so that edge is aligned (if it isn't already), set the UV grid size so a grid line is on the part of the texture you want to align to the other edge of the face, and then drag that grid line until it snaps to that edge.

This video isn't about that (it's really more about avoiding using the UV editor as much as possible) but there's a really quick demo of the above at the timestamp

You can change colours in View -> Preferences -> Colors, but I couldn't find one for that specific outline, maybe you'll have better luck.