TODO

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PRIORITY: HIGH
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o Set some limits on the view's width and height, particularly when zooming. If
the view grows a lot but the window remains small, the graph becomes a mess.
o Improve dataset plotting.
o Implement ticks & graphs labeling.
o Implement ticks, axes & grid as GsPlot items.
o Keyboard movement & zooming.
o Don't draw points outside view's limits. This is causing a lot of graphic
glitches such as the coordinate axes appearing when scrolling (a lot) to the left
or right, or function getting evaluated with strange x values, resulting in points
showing in wrong locations.
o Handle non-numerical values (i.e. the graph 1/x becomes a mess because 1/0 is evaluated).
o Implement some sort of 'continuity detection' for non-continuous functions like 1/x (i.e. avoid joining the last point < 0 with the first one > 0)

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PRIORITY: NORMAL
=================

o Abstract plotting details by using a GsPlot object which can be inherited by GsFunctionPlot
and GsDatasetPlot. Create new plots: vector fields, polar curves, etc. [DONE]
o Create API methods in order to allow for plot removal.
o Implement tooltips for GsGraph. The tooltips could be used to display
the (x,y) coords of the location the cursor is pointing at.

=================
PRIORITY: LOW
=================

o Allow for modification of point radius and zoom factor.
o Cairo support.
o Create a graphic quality comparison with other plotting widgets and
software (GtkExtra, Winplot, etc.)
o GsFunctionPlot: allow function's domain to be locked on [a,b].