Issue244: GetDefaultEntry returns first expression, without semicolon

[dilijev]

From #244

When GUI commands choose which expression to use (Plot2d..., Simplify...) etc, and a cell is active but no selection is made, GetDefaultEntry would copy the entire text of the active cell, but this always wrong because it includes the semicolon or dollar sign, which causes a syntax error.

This patch fixes this issue, as well as only allowing the first expression in a cell to be copied in, because these functions cannot deal with multiple expressions either.

[dilijev]

@andrejv

The fix I made will work in all cases where the cell in question contains one statement, examples:

x+1;
y+2$

However if the cell includes more than one statement, examples:

x+1; y+2$
x+1$ y+2;

The only input that will be copied is that up to the first ; or $, in both examples above: x+1

The patch still improves the behavior to prevent errors, but I wonder what the user will think happened to the rest of the input. Would they expect the same operation to be executed on both inputs in the cell? If so, what should the interface look like for that? Should we launch e.g. the Plot2d dialog once for each input? Should we display the input as shown in the cell, and then evaluate the function once for each input that was in that cell?

Alternatively, should the expression that is chosen be the one that is first in the cell, or the one that the cursor is within? Consider the examples above, if the cursor is located within the second expression, should that expression, y+2, be selected, or should the first expression in the cell be selected? Which is more logical? Which is more natural?

Since selecting the first expression, regardless of cursor position, was a bit easier to implement, the patch includes a fix which exhibits that behavior, but the actual functionality of the feature is, IMO, up for discussion.