linked axes prototype

implot.cpp

@@ -411,6 +411,16 @@ void FitPoint(const ImPlotPoint& p) {
     }
 }
 
+void PushLinkedAxis(ImPlotAxis& axis) {
+    if (axis.LinkedMin) { *axis.LinkedMin = axis.Range.Min; }
+    if (axis.LinkedMax) { *axis.LinkedMax = axis.Range.Max; }
+}
+
+void PullLinkedAxis(ImPlotAxis& axis) {
+    if (axis.LinkedMin) { axis.Range.Min = *axis.LinkedMin; }
+    if (axis.LinkedMax) { axis.Range.Max = *axis.LinkedMax; }    
+}
+
 //-----------------------------------------------------------------------------
 // Coordinate Utils
 //-----------------------------------------------------------------------------
@@ -675,6 +685,16 @@ bool BeginPlot(const char* title, const char* x_label, const char* y_label, cons
 
     // NextPlotData -----------------------------------------------------------
 
+    // linked axes
+    plot.XAxis.LinkedMin = gp.NextPlotData.LinkedXmin;
+    plot.XAxis.LinkedMax = gp.NextPlotData.LinkedXmax;
+    PullLinkedAxis(plot.XAxis);
+    for (int i = 0; i < IMPLOT_Y_AXES; ++i) {
+        plot.YAxis[i].LinkedMin = gp.NextPlotData.LinkedYmin[i];
+        plot.YAxis[i].LinkedMax = gp.NextPlotData.LinkedYmax[i];
+        PullLinkedAxis(plot.YAxis[i]);
+    }
+
     if (gp.NextPlotData.HasXRange) {
         if (just_created || gp.NextPlotData.XRangeCond == ImGuiCond_Always) {
             plot.XAxis.Range = gp.NextPlotData.X;
@@ -1649,6 +1669,13 @@ void EndPlot() {
         ImGui::PopID();
     }
 
+
+    // LINKED AXES ------------------------------------------------------------
+
+    PushLinkedAxis(plot.XAxis);
+    for (int i = 0; i < IMPLOT_Y_AXES; ++i)
+        PushLinkedAxis(plot.YAxis[i]);
+
     // CLEANUP ----------------------------------------------------------------
 
     // reset the plot items for the next frame
@@ -1697,6 +1724,18 @@ void SetNextPlotLimitsY(double y_min, double y_max, ImGuiCond cond, int y_axis)
     gp.NextPlotData.Y[y_axis].Max = y_max;
 }
 
+void LinkNextPlotLimits(double* xmin, double* xmax, double* ymin, double* ymax, double* ymin2, double* ymax2, double* ymin3, double* ymax3) {
+    ImPlotContext& gp = *GImPlot;
+    gp.NextPlotData.LinkedXmin    = xmin;
+    gp.NextPlotData.LinkedXmax    = xmax;
+    gp.NextPlotData.LinkedYmin[0] = ymin;
+    gp.NextPlotData.LinkedYmax[0] = ymax;
+    gp.NextPlotData.LinkedYmin[1] = ymin2;
+    gp.NextPlotData.LinkedYmax[1] = ymax2;
+    gp.NextPlotData.LinkedYmin[2] = ymin3;
+    gp.NextPlotData.LinkedYmax[2] = ymax3;
+}
+
 void FitNextPlotAxes(bool x, bool y, bool y2, bool y3) {
     ImPlotContext& gp = *GImPlot;
     IM_ASSERT_USER_ERROR(gp.CurrentPlot == NULL, "FitNextPlotAxes() needs to be called before BeginPlot()!");

implot.h

@@ -376,14 +376,17 @@ void PlotText(const char* text, double x, double y, bool vertical = false, const
 //-----------------------------------------------------------------------------
 
 // Set the axes range limits of the next plot. Call right before BeginPlot(). If ImGuiCond_Always is used, the axes limits will be locked.
-void SetNextPlotLimits(double x_min, double x_max, double y_min, double y_max, ImGuiCond cond = ImGuiCond_Once);
+void SetNextPlotLimits(double xmin, double xmax, double ymin, double ymax, ImGuiCond cond = ImGuiCond_Once);
 // Set the X axis range limits of the next plot. Call right before BeginPlot(). If ImGuiCond_Always is used, the X axis limits will be locked.
-void SetNextPlotLimitsX(double x_min, double x_max, ImGuiCond cond = ImGuiCond_Once);
+void SetNextPlotLimitsX(double xmin, double xmax, ImGuiCond cond = ImGuiCond_Once);
 // Set the Y axis range limits of the next plot. Call right before BeginPlot(). If ImGuiCond_Always is used, the Y axis limits will be locked.
-void SetNextPlotLimitsY(double y_min, double y_max, ImGuiCond cond = ImGuiCond_Once, int y_axis = 0);
+void SetNextPlotLimitsY(double ymin, double ymax, ImGuiCond cond = ImGuiCond_Once, int y_axis = 0);
+// Links the next plot axes to external range. Set to NULL for no linkage. The pointer data must remain valid until the matching call EndPlot.
+void LinkNextPlotLimits(double* xmin, double* xmax, double* ymin, double* ymax, double* ymin2 = NULL, double* ymax2 = NULL, double* ymin3 = NULL, double* ymax3 = NULL);
 // Fits the next plot axes to all plotted data if they are unlocked (equivalent to double-clicks).
 void FitNextPlotAxes(bool x = true, bool y = true, bool y2 = true, bool y3 = true);
 
+
 // Set the X axis ticks and optionally the labels for the next plot.
 void SetNextPlotTicksX(const double* values, int n_ticks, const char** labels = NULL, bool show_default = false);
 void SetNextPlotTicksX(double x_min, double x_max, int n_ticks, const char** labels = NULL, bool show_default = false);

implot_demo.cpp

@@ -637,6 +637,25 @@ void ShowDemoWindow(bool* p_open) {
         }
     }
     //-------------------------------------------------------------------------
+    if (ImGui::CollapsingHeader("Linked Axes")) {
+        static double xmin = 0, xmax = 1, ymin = 0, ymax = 1;
+        static bool linkx = true, linky = true;
+        t_float data[2] = {0,1};
+        ImGui::Checkbox("Link X", &linkx);
+        ImGui::SameLine();
+        ImGui::Checkbox("Link Y", &linky);
+        ImPlot::LinkNextPlotLimits(linkx ? &xmin : NULL , linkx ? &xmax : NULL, linky ? &ymin : NULL, linky ? &ymax : NULL);
+        if (ImPlot::BeginPlot("Plot A")) { 
+            ImPlot::PlotLine("Line",data,2);
+            ImPlot::EndPlot(); 
+        }
+        ImPlot::LinkNextPlotLimits(linkx ? &xmin : NULL , linkx ? &xmax : NULL, linky ? &ymin : NULL, linky ? &ymax : NULL);
+        if (ImPlot::BeginPlot("Plot B")) { 
+            ImPlot::PlotLine("Line",data,2);
+            ImPlot::EndPlot(); 
+        }
+    }
+    //-------------------------------------------------------------------------
     if (ImGui::CollapsingHeader("Querying")) {
         static ImVector<t_float2> data;
         static ImPlotLimits range, query;

implot_internal.h

@@ -249,6 +249,8 @@ struct ImPlotAxis
     bool            Dragging;
     bool            HoveredExt;
     bool            HoveredTot;
+    double*         LinkedMin;
+    double*         LinkedMax;
 
     ImPlotAxis() {
         Flags      = PreviousFlags = ImPlotAxisFlags_Default;
@@ -257,6 +259,7 @@ struct ImPlotAxis
         Dragging   = false;
         HoveredExt = false;
         HoveredTot = false;
+        LinkedMin  = LinkedMax = NULL;
     }
 };
 
@@ -356,19 +359,26 @@ struct ImPlotNextPlotData
     bool        ShowDefaultTicksY[IMPLOT_Y_AXES];
     bool        FitX;
     bool        FitY[IMPLOT_Y_AXES];
+    double*     LinkedXmin;
+    double*     LinkedXmax;
+    double*     LinkedYmin[IMPLOT_Y_AXES];
+    double*     LinkedYmax[IMPLOT_Y_AXES];
 
     ImPlotNextPlotData() {
         HasXRange         = false;
         ShowDefaultTicksX = true;
         FitX              = false;
+        LinkedXmin = LinkedXmax = NULL;
         for (int i = 0; i < IMPLOT_Y_AXES; ++i) {
             HasYRange[i]         = false;
             ShowDefaultTicksY[i] = true;
             FitY[i]              = false;
+            LinkedYmin[i] = LinkedYmax[i] = NULL;
         }
     }
 };
 
+
 // Temporary data storage for upcoming item
 struct ImPlotItemStyle {
     ImVec4       Colors[5]; // ImPlotCol_Line, ImPlotCol_Fill, ImPlotCol_MarkerOutline, ImPlotCol_MarkerFill, ImPlotCol_ErrorBar
@@ -547,6 +557,11 @@ inline bool FitThisFrame() { return GImPlot->FitThisFrame; }
 // Extends the current plots axes so that it encompasses point p
 void FitPoint(const ImPlotPoint& p);
 
+// Updates pointers for linked axes from axis internal range
+void PushLinkedAxis(ImPlotAxis& axis);
+// Updates axis internal range from points for linked axes
+void PullLinkedAxis(ImPlotAxis& axis);
+
 //-----------------------------------------------------------------------------
 // [SECTION] Legend Utils
 //-----------------------------------------------------------------------------