Zoom via external slider (as a poor mans replacement for multi touch pinch to zoom)

[stohn]

Hi Evan,

First of all, I have to say a big THANK YOU for this excellent library. Whenever I wanted another extra "bells and whistles" it was already covered and just a simple look at the demo, and "lift some code" from there.

The last major item I still need to tackle for my project is an easy way to zoom the diagram. The final version should run on a Raspberry PI with its own (multi) touch screen (panning already works with the normal touch to mouse translation from the OS). I know this problem has been brought up a few times before (here and in the ImGui project itself), but somehow I really need to find a solution or workaround.

I've already had an extensive look at SDL_MultiGesture(), but I'm having a hard time running even a simple SDL test on my particular hardware (not to mention multiple platform support...).

So my idea was to just add a horizontal and vertical slider next to the plot area and try to use them to zoom. That kinda worked, but for some reason I never figured out how to use the axis limits / links / ... (I tried many things) properly to make it work and feel "normal".

I think that ImPlot's public API is just not sufficient to achieve this.

Do you have any suggestions or ideas on how to achieve this?

Thanks in advance,

Maik

[unknown321]

You can do it like this with buttons, should be easy to adapt to sliders.

// out of the draw loop
auto cond = ImPlotCond_Once;

...

if (ImGui::Button("Shift to the left")) {
	cond = ImPlotCond_Always;
	xMin = xMin - 10;
	xMax = xMax - 10;
}

if (ImGui::Button("Zoom in")) {
	cond = ImPlotCond_Always;
	xMin = xMin + 10;
	xMax = xMax - 10;
	yMin = yMin + 10;
	yMax = yMax - 10;
}

if (ImPlot::BeginPlot("##myplot", ImVec2(200,200), ImPlotFlags_None)) {
	ImPlot::SetupAxesLimits(xMin, xMax, yMin, yMax, cond);
	// your plot lines here
}

if (cond != ImPlotCond_Once) {
    cond = ImPlotCond_Once;
}