Hello,
I found Geany some time ago, searching for a simple, small IDE, and while it definitely looks very nice, the thing that surprised me the most was how incredibly slow the editor was. I tried many different editors before, and while GTK+ based ones have always been slower than others, with higher CPU overhead, I've never seen anything as slow as Geany (and SciTE, to be fair) - for example, in a C++ file, holding the left/right keys (so the cursor keeps going to left/right) consumes over 50% of CPU and it even stutters, stumbles on brackets, holding the up/down keys is even more CPU intensive, the editor actually cannot keep up with the cursor movement, the same with scrolling (which is slow and laggy - the scrollbar cannot update itself fast enough, it jumps instead of moving continuously), and also mouse selection - when I select a larger part of the source code, like a function with 20+ lines, CPU usage goes to 100% and the selection lags, too, it cannot keep up with the mouse movement. In a plain text file (with no syntax highlighting), the CPU usage is naturally lower, it does not lag so much. The extremely slow editor also affects the main menu redrawing performance - when a blank file is open in the editor, the menu can redraw as fast as in any other GTK+ app (i.e. fast enough), with a plain text file, it's slower, but when a .cpp file is loaded, again the redrawing is extremely slow, the menu cannot keep up with the mouse (when I ride through the menu from left to right, for example).
Now, I know it sounds as if my computer is broken, but when I compare it with other editors: for example in emacs, the CPU usage while holding the arrow keys is about 0% (even in the GTK+ version), other, more modern and heavyweight editors like the Kate-based ones (KDE) consume about 2-3 times less CPU cycles than Geany does for these basic tasks like selection, typing and scrolling, the same applies even to the gedit editor in GNOME, with its syntax higlighting - even though it's GTK+ based, there are no lags and 100% CPU usage at all.
Is there anything that can be done about it? Or is it just my computer? It's a 2.4 GHz P4 with the nv driver for X.org, tried it on Debian and Arch Linux, which are both pretty lightweight to begin with... Is the Scintilla library really so inefficient? Because like I said, the only other editor I've tried that's as slow as Geany was SciTE, so it looks like it's Scintilla's fault...