Support Board

void CenterTheChart(SCStudyInterfaceRef sc)
{
  sc.BaseGraphScaleConstRange = sc.ChartRegion1BottomCoordinate * 0.233387358;
  sc.BaseGraphScaleRangeTop = sc.Close[sc.IndexOfLastVisibleBar] + sc.BaseGraphScaleConstRange*4/9.0;
  sc.BaseGraphScaleRangeBottom = sc.Close[sc.IndexOfLastVisibleBar] - sc.BaseGraphScaleConstRange*5/9.0;
}

#include "sierrachart.h"

SCDLLName("Adaptive Constant Range by Height")

SCSFExport scsf_AdaptiveConstantRangeAuto(SCStudyInterfaceRef sc)
{
// Persistent storage
int& r_BaselineHeight = sc.GetPersistentInt(0);
float& r_BaselineConstRange = sc.GetPersistentFloat(1);
int& r_LastHeight = sc.GetPersistentInt(2);
int& r_BaselineCaptured = sc.GetPersistentInt(3); // 0 = not yet
float& r_LastValueWeSet = sc.GetPersistentFloat(4); // last value written by the study

if (sc.SetDefaults)
{
sc.GraphName = "Adaptive Constant Range by Height (Auto)";
sc.StudyDescription =
"Keeps visual bar size constant when the chart window is resized. "
"Automatically captures the current height + Constant Range as baseline. "
"If you later change the Constant Range manually, the study re-learns "
"the new value as the new baseline. "
"Only sc.BaseGraphScaleConstRange is ever modified.";

sc.AutoLoop = 0;
sc.GraphRegion = 0;
sc.UpdateAlways = 1;
sc.CalculationPrecedence = LOW_PREC_LEVEL;

return;
}

// Current height of Chart Region 1
int CurrentHeight = sc.ChartRegion1BottomCoordinate - sc.ChartRegion1TopCoordinate;
if (CurrentHeight <= 10)
return;

float CurrentConstRange = sc.BaseGraphScaleConstRange;

// ------------------------------------------------------------------
// 1. Detect that the user manually changed the Constant Range
// ------------------------------------------------------------------
// If the value currently in the chart is different from the last value
// the study itself wrote, the user must have changed it.
const float EPSILON = 0.00001f;
bool UserChangedRange = (r_BaselineCaptured != 0) &&
(fabsf(CurrentConstRange - r_LastValueWeSet) > EPSILON);

// ------------------------------------------------------------------
// 2. Capture / re-capture baseline
// ------------------------------------------------------------------
if (r_BaselineCaptured == 0 || sc.IsFullRecalculation || UserChangedRange)
{
if (CurrentConstRange > 0.0f)
{
r_BaselineHeight = CurrentHeight;
r_BaselineConstRange = CurrentConstRange;
r_LastHeight = CurrentHeight;
r_LastValueWeSet = CurrentConstRange; // we did not change it, user did
r_BaselineCaptured = 1;

// Optional confirmation
/*
SCString msg;
msg.Format("Baseline %s: Height=%d ConstRange=%.5f",
UserChangedRange ? "updated by user" : "captured",
r_BaselineHeight, r_BaselineConstRange);
sc.AddMessageToLog(msg, 0);
*/
}
return;
}

// ------------------------------------------------------------------
// 3. Only act when the window height has actually changed
// ------------------------------------------------------------------
if (CurrentHeight == r_LastHeight)
return;

r_LastHeight = CurrentHeight;

// Calculate new range while preserving the visual density of the baseline
float NewConstRange = r_BaselineConstRange * ((float)CurrentHeight / (float)r_BaselineHeight);

// *** THE ONLY LINE THAT WRITES TO THE CHART ***
sc.BaseGraphScaleConstRange = NewConstRange;

// Remember what we just wrote so we can detect future manual changes
r_LastValueWeSet = NewConstRange;
}