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Speed-independent scope trail persistence (XY plots) #240

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33 changes: 24 additions & 9 deletions src/com/lushprojects/circuitjs1/client/Scope.java
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Original file line number Diff line number Diff line change
Expand Up @@ -262,6 +262,10 @@ class Scope {
Canvas imageCanvas;
Context2d imageContext;
int alphaCounter =0;
// XY-plot trail persistence (wall-clock ms). 0 = instant erase (no trail).
int trailPersistence = 200;
static final int DEFAULT_TRAIL_PERSISTENCE = 200;
long lastTrailTime;
// scopeTimeStep to check if sim timestep has changed from previous value when redrawing
double scopeTimeStep;
double scale[]; // Max value to scale the display to show - indexed for each value of UNITS - e.g. UNITS_V, UNITS_A etc.
Expand Down Expand Up @@ -1054,17 +1058,25 @@ void draw2d(Graphics g) {
g.context.translate(rect.x, rect.y);
g.clipRect(0, 0, rect.width, rect.height);

alphaCounter++;

if (alphaCounter>2) {
// fade out plot
alphaCounter=0;
imageContext.setGlobalAlpha(0.01);
if (app.isPrintable()) {
// Wall-clock-based exponential fade. alpha = 1 - exp(-elapsed/persistence)
// makes the trail look the same across simulation speeds: at 60fps a 200ms
// persistence drops a pixel by 1-exp(-16/200) = 7.7% per frame; at 30fps
// the same persistence drops by 1-exp(-33/200) = 15% per frame, so total
// decay over a fixed wall-clock interval is constant.
long now = System.currentTimeMillis();
long elapsed = (lastTrailTime == 0) ? 16 : (now - lastTrailTime);
lastTrailTime = now;
double fadeAlpha;
if (trailPersistence <= 0)
fadeAlpha = 1.0; // instant erase = no trail
else
fadeAlpha = 1.0 - Math.exp(-elapsed / (double) trailPersistence);
if (fadeAlpha > 0) {
imageContext.setGlobalAlpha(fadeAlpha);
if (app.isPrintable())
imageContext.setFillStyle("#ffffff");
} else {
else
imageContext.setFillStyle("#000000");
}
imageContext.fillRect(0,0,rect.width,rect.height);
imageContext.setGlobalAlpha(1.0);
}
Expand Down Expand Up @@ -2211,6 +2223,8 @@ void dumpXml(Document doc, Element root) {

if (text != null)
xmlElm.setAttribute("x", text);
if (trailPersistence != DEFAULT_TRAIL_PERSISTENCE)
XMLSerializer.dumpAttr(xmlElm, "tp", trailPersistence);
}

void undumpXml(XMLDeserializer xml) {
Expand All @@ -2226,6 +2240,7 @@ void undumpXml(XMLDeserializer xml) {
position = xml.parseIntAttr("p", 0);
manDivisions = xml.parseIntAttr("md", 8);
text = xml.parseStringAttr("x", (String)null);
trailPersistence = xml.parseIntAttr("tp", DEFAULT_TRAIL_PERSISTENCE);
// Read trigger settings from parent <o> element before iterating children,
// because parseChildElement() changes the XML context to child <p> elements
int xmlTriggerMode = xml.parseIntAttr("triggerMode", TRIGGER_FREERUN);
Expand Down
26 changes: 24 additions & 2 deletions src/com/lushprojects/circuitjs1/client/ScopePropertiesDialog.java
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Expand Up @@ -58,7 +58,8 @@ public class ScopePropertiesDialog extends Dialog implements ValueChangeHandler<
CheckBox elmInfoBox;
TextBox labelTextBox, manualScaleTextBox, divisionsTextBox;
Button applyButton, scaleUpButton, scaleDownButton;
Scrollbar speedBar,positionBar;
Scrollbar speedBar, positionBar, trailBar;
Label trailLabel;
Scope scope;
Grid grid, vScaleGrid, hScaleGrid;
int nx, ny;
Expand Down Expand Up @@ -518,6 +519,20 @@ public void onClick(ClickEvent event) {
viBox.addValueChangeHandler(this);
addItemToGrid(grid, xyBox = new ScopeCheckBox(Locale.LS("Plot X/Y"), "plotxy"));
xyBox.addValueChangeHandler(this);
Grid trailGrid = new Grid(1, 3);
trailGrid.setWidget(0, 0, new Label(Locale.LS("Trail Persistence (ms)")));
// Range 0..2000 ms; step 50; 0 = instant erase (no trail)
trailBar = new Scrollbar(Scrollbar.HORIZONTAL, scope.trailPersistence, 1, 0, 2050, new Command() {
public void execute() {
scope.trailPersistence = trailBar.getValue();
setTrailLabel();
}
});
trailGrid.setWidget(0, 1, trailBar);
trailLabel = new Label("");
trailGrid.setWidget(0, 2, trailLabel);
fp.add(trailGrid);
setTrailLabel();
if (transistor) {
addItemToGrid(grid, vceIcBox = new ScopeCheckBox(Locale.LS("Show Vce vs Ic"), "showvcevsic"));
vceIcBox.addValueChangeHandler(this);
Expand Down Expand Up @@ -625,7 +640,14 @@ void updateRowVisibility() {
void setScopeSpeedLabel() {
scopeSpeedLabel.setText(CircuitElm.getUnitText(scope.calcGridStepX(), "s")+"/div");
}


void setTrailLabel() {
if (scope.trailPersistence <= 0)
trailLabel.setText(Locale.LS("none"));
else
trailLabel.setText(scope.trailPersistence + " ms");
}

void addItemToGrid(Grid g, FocusWidget scb) {
g.setWidget(ny, nx, scb);
if (++nx >= grid.getColumnCount()) {
Expand Down
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