Number of major ticks strategy

[Murphy, S. <sm...@wa...>]

I'm having an issue where when I first setup a plot, the left & right scale widgets are set up pretty nicely - they have a reasonable number of major tick marks. But I allow the user to resize the plot vertically. Growing the plot isn't really a problem, but when the user shrinks the plot I think I need to reduce the number of major tick marks just to keep them from getting to crammed in on each other.

I was just wondering if anyone has already come up with a strategy for handling this (or if I'm just missing something in the API that already does this)?

My thought was overriding resizeEvent() and then based on the new size, dynamically call "something" - not sure which function is best to call here, maybe just call QwtPlot::setAxisScale() again with the same values as before to get the updateAxes() to recalculate the scale for me?

My requirements are:

-        Linear scale

-        I need to specify the min/max values of the scale AND see those exact values on the top & bottom of the scale widget. So if for example, I set the range from 17 to 43, the label for the bottommost tick mark needs to say 17, and the label for the topmost needs to say 43. Similarly if I set it from -20 to 100, I need to see -20 and 100 at the two ends of the scale.

-        I don't particularly care whether the tickmarks in between the min & max are based on multiples of 2,5, or 10 based, or if they are based on some other multiple

-        Need to be able to dynamically decrease/increase number of tick marks as the height of the plot changes with the goal being a "decent" amount of pixel space between major ticks, even if that means we drop down to only 2 major tick marks for the entire scale - the min & the max values, I always need to see those two.

Sean Murphy
Sr. Project Engineer
Walbro LLC
4144 Doerr Rd
Cass City, MI 48726
ph. 989 872 7274
cell 734 223 8975
fax. 989 872 3782
sm...@wa...<mailto:sm...@wa...>

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