I agree with Eric that this might not be worth a lot of time. OTOH, an interface that would always promote to Queen, does ot seem acceptable to most users. I tried that once for premove, and even that was received very negatively. The problem with the promotion popup is that you are annoyed by it in 999 cases, where you need it in only one. The aim is to remove that annoyance in the 999 cases, without completely sacrificing the exceptional case, which auto-queen does.
Plus that the current promotion popup is inadequate for many variants, and fixing that would take time too. This is why I was looking for a simple solution. Preferably one that would make porting to GTK easier, by removing front-end code, rather than adding new front-end code for buttons etc. Note that what I implemented so far was alsmost completely back-end, except that the "mouse moves with left button down" hadler, which already existed for piece dragging, lived entirely in the front-ends, so I needed to put a call in those to the new bac-end code. Based on what is said so far I have two new ideas: 1) pre-promote: Instead of selecting the promotion piece after you indicate the Pawn move, you could do it in advance, as Arun suggests. Except that in stead of off-board buttons, I would prefer the mouse- sweep mechanism for that also. E.g. right-click a 7th-rank Pawn, drag the mouse down to cycle through the choices on that square in full size (starting with N, as Q is default), and let the up-click determine the choice, after which it reverts to Pawn, and you can perform the move. This would count as selection of the Pawn, so you can now perform the move by just left-clicking the to-square. Or you can drag-drop the Pawn. Doing any other move would reset the auto-choice to Q. But the opponent move would not, so that you can do this in the opponen't time even when premove is off. 2) detour selection Pawns only move forward. When you grab a 7th-rank Pawn with the left mouse button, it already changes to a Queen before you release it on the to-square. When you release it on the same square it reverts to Pawn (you might have changed your mind and want to grab another piece), but it would be interpreted as the first click of a click-click move, and the flashing of the Queen would just act as a reminder that you are going to promote to Q. Dragging it would drag the Queen image rather than a Pawn. But dragging it (sufficiently far) backwards, would change the image of the piece you are dragging, from Q to N, B, R, (K), Q, ... When it becomes the piece you want, you drag it forward again, and release it on the to-square. A simplified implementation of this would make the initial direction of mouse movement decide what you are going to do: moving the Pawn (which looks like a Queen) or selecting a promotion piece. Forward motion would drag the Queen to the promotion square, if you did not want a Queen this would warn you off, and you would release on the from-square to abort. Backward initial motion would go into the same piece-selection loop my existing patch does now, but on the from-square rather than the to-square. Once you start cycling through the pieces you could cycle both ways, in case you overshoot; it would never revert to dragging again. The from-square reverts to a (selected) Pawn once you release the left button to indicate your choice. You can then perform the move by left-clicking to-square, or you could grab the Pawn (which would change into the newly selected piece as soon as you touch it), and drag it (forward!) to the to-square. Dragging backwards would just restart you in the selection loop again, in case you see that the choice was not what you intended after all, and want to correct it. Come to think of it: I might like this 'simplified' implementation best. (Because you can cycle through the pieces in both directions.) Only problem is how to handle Shogi, where it is not obvious that a piece offers promotion choice at the time you grab it, and promoting pieces can move both ways...
