@dinnaset
dinasset wrote:
a "one click healing tool"
that is: a tool you select and use directly on the area from which you want to remove a spot: the spot is replaced by the colours-structure of the surrounding area. This grants to override the defect with the most appropriate texture.
The resynthesizer plug-in
http://registry.gimp.org/node/25219 with the "Heal Selection" script comes pretty close to what you are looking for. Admittedly it takes about four clicks: make a selection, hit Filters -> Enhance -> Heal Selection -> OK. But it performs the task exactly as you described - it can be slow on very large areas however.
Also if you have already just healed one selection, you can make another and this time just hit CTRL+F to repeat the Heal Selection Filter. Would that count as a single click? I guess you could also use the Quick Mask (shift Q) to create selections by painting.
Perhaps if such a tool as you envisage were based on Resynthesizer your dream could become a reality. The tool would only have to make a selection (as per Quick Mask) and then run the resynthesizer Heal Selection script as soon as the mouse button is released.
There's also the Healing Tool for smaller spots/blemishes, select the healing tool, CTRL+Click to create a sample point, paint over the blemish/spot you want to remove. But that one doesn't choose automatically what to fill with, you still need to select a sample/target first - although the choice of target is not crucial as it is with the Clone Tool.