ProEssentials WPF — Log-Log Axes & Quick Annotation Drag Measure

A ProEssentials v10 WPF .NET 8 demonstration of two advanced PesgoWpf features: intelligent logarithmic axes that restructure intelligently on zoom, and a live drag measurement tool built with the Quick Annotation mechanism.

➡️ gigasoft.com/examples

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What This Demonstrates

Feature	How to See It
Log-Log axes	Scroll the mouse wheel — watch grid lines restructure at decade boundaries as you zoom through orders of magnitude
Quick Annotation drag measure	Left-click and drag — a live measurement rectangle appears showing X and Y deltas, updated every MouseMove with no chart rebuild

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ProEssentials Features Demonstrated

Log-Log Axes

Both axes use ScaleControl.Log. ProEssentials selects intelligent logarithmic grid numbers automatically at any zoom level, always landing on clean powers of ten and their subdivisions:

Pesgo1.PeGrid.Configure.XAxisScaleControl = ScaleControl.Log;
Pesgo1.PeGrid.Configure.YAxisScaleControl = ScaleControl.Log;

Mouse wheel zooms both axes simultaneously:

Pesgo1.PeUserInterface.Allow.Zooming = AllowZooming.None; // left-drag reserved for measurement
Pesgo1.PeUserInterface.Scrollbar.MouseWheelFunction = MouseWheelFunction.HorizontalVerticalZoom;
Pesgo1.PeUserInterface.Scrollbar.MouseWheelZoomSmoothness = 8;

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Quick Annotation Drag Measurement Tool

Quick annotations are graph annotations that render via an optimized overlay path, avoiding full chart rebuilds. They are ideal for transient UI that updates every MouseMove.

Required Setup

In WPF, PesgoWpf automatically manages the CacheBmp2 secondary buffer and improved cursor rendering — these properties are not exposed on the WPF interface and require no explicit setup.

The only mouse wheel zoom requirement is pairing MouseWheelFunction with the matching scrollbar flags:

Pesgo1.PeUserInterface.Scrollbar.ScrollingHorzZoom  = true;
Pesgo1.PeUserInterface.Scrollbar.ScrollingVertZoom  = true;
Pesgo1.PeUserInterface.Scrollbar.MouseWheelFunction = MouseWheelFunction.HorizontalVerticalZoom;

MouseWheelFunction.HorizontalVerticalZoom requires both flags set explicitly — without them the wheel cannot zoom out and only one axis responds.

Negative Type Formula

Any GraphAnnotationType value becomes a quick annotation by negating it:

// Normal annotation — baked into cached image, requires ResetImage to change:
Graph.Type[i] = (int)GraphAnnotationType.TopLeft;

// Quick annotation — overlay only, no chart rebuild needed:
Graph.Type[i] = ((int)GraphAnnotationType.TopLeft + 1) * -1;

When ShowingQuickAnnotations = true, only negative-type annotations are rendered, drawn on top of the primary cached chart image.

Measurement Overlay — 6 Annotations

Index	Type	Purpose
[0]	TopLeft (negative)	Top-left bound of the selection rectangle
[1]	BottomRight (negative)	Bottom-right bound
[2]	RoundRectFill (negative)	Semi-transparent filled background
[3]	RoundRectMedium (negative)	White border outline
[4]	NoSymbol + |c text (negative)	X-delta label, centered horizontally
[5]	NoSymbol + |D text (negative)	Y-delta label, centered vertically (right edge)

Showing and Hiding

// MouseMove — trigger overlay redraw (no chart rebuild):
Pesgo1.PeAnnotation.ShowingQuickAnnotations = true;
Pesgo1.Invalidate();
Pesgo1.Refresh();

// MouseUp — clear overlay:
Pesgo1.PeAnnotation.ShowingQuickAnnotations = false;
Pesgo1.PeAnnotation.HidingQuickAnnotations  = true;
Pesgo1.Invalidate();
Pesgo1.Refresh();

Log-Scale Label Centering

On log axes the visual center of a span is the geometric mean, not the arithmetic mean. Delta labels use geometric centering so they appear visually centered within the selection at any zoom level:

double centeredXLog = (Math.Log10(fX) + Math.Log10(_dragStartX)) / 2.0;
double centeredX    = Math.Pow(10.0, centeredXLog);

Text Justification Codes

Code	Meaning
|c	Centered horizontally, bottom anchor (text above the point)
|D	Centered vertically on right side — 90° rotated text, right edge

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ConvPixelToGraph — Pixel to Data Coordinates

Mouse pixel positions are converted to data-unit coordinates using ConvPixelToGraph, then clamped to the visible axis extents:

int nA = 0, nX = (int)pt.X, nY = (int)pt.Y;
double fX = 0, fY = 0;
Pesgo1.PeFunction.ConvPixelToGraph(ref nA, ref nX, ref nY,
                                    ref fX, ref fY, false, false, false);

// Clamp to current visible range
fX = Math.Max(Pesgo1.PeGrid.Configure.ManualMinX,
     Math.Min(Pesgo1.PeGrid.Configure.ManualMaxX, fX));

ManualMinX/MaxX/MinY/MaxY are only valid after the chart has rendered its first image — never read them during initialization.

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Controls

Input	Action
Mouse wheel	Zoom both axes (log-scale aware, smooth)
Left-click drag	Live drag measurement overlay
Right-click	Context menu — export, print, customize

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Prerequisites

• Visual Studio 2022
• .NET 8 SDK

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How to Run

1. Clone this repository
2. Open LogLogDragMeasure.sln in Visual Studio 2022
3. Build → Rebuild Solution (NuGet restore is automatic)
4. Press F5

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NuGet Package

References ProEssentials.Chart.Net80.x64.Wpf. Package restore is automatic on build.

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Related Examples

• WPF Multi-Axis Layout Explorer
• WPF Mouse Interaction Hotspots
• All Examples — GigasoftInc on GitHub
• Full Evaluation Download
• gigasoft.com

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License

Example code is MIT licensed. ProEssentials requires a commercial license for continued use.