add previous plot and such

implot.cpp

@@ -384,6 +384,7 @@ void SetCurrentContext(ImPlotContext* ctx) {
 
 void Initialize(ImPlotContext* ctx) {
     Reset(ctx);
+    ctx->CurrentPlot = ctx->PreviousPlot = NULL;
     ctx->Colormap = GetColormap(ImPlotColormap_Default, &ctx->ColormapSize);
 }
 
@@ -417,6 +418,7 @@ void Reset(ImPlotContext* ctx) {
     ctx->DigitalPlotItemCnt = 0;
     ctx->DigitalPlotOffset = 0;
     // nullify plot
+    ctx->PreviousPlot = ctx->CurrentPlot;
     ctx->CurrentPlot  = NULL;
     ctx->CurrentItem  = NULL;
     ctx->PreviousItem = NULL;
@@ -436,6 +438,10 @@ ImPlotPlot* GetCurrentPlot() {
     return GImPlot->CurrentPlot;
 }
 
+ImPlotPlot* GetCurrentOrPreviousPlot() {
+    return GImPlot->CurrentPlot == NULL ? GImPlot->PreviousPlot : GImPlot->CurrentPlot;
+}
+
 void BustPlotCache() {
     GImPlot->Plots.Clear();
 }
@@ -2914,27 +2920,37 @@ bool DragPoint(const char* id, double* x, double* y, bool show_label, const ImVe
 bool BeginDragDropTargetEx(int id, const ImRect& rect) {
     ImGuiContext& G  = *GImGui;
     const ImGuiID ID = G.CurrentWindow->GetID(id);
-    if (ImGui::ItemAdd(rect, ID, &rect) &&
+    if (ImGui::ItemAdd(rect, ID, &rect) && ImGui::BeginDragDropTarget())
-        ImGui::BeginDragDropTarget())
         return true;
     return false;
 }
 
 bool BeginDragDropTarget() {
-    return BeginDragDropTargetEx(IMPLOT_ID_PLT, GImPlot->CurrentPlot->PlotRect);
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
+    if (plt == NULL) 
+        return false;
+    return BeginDragDropTargetEx(IMPLOT_ID_PLT, plt->PlotRect);
 }
 
 bool BeginDragDropTargetX() {
-    return BeginDragDropTargetEx(IMPLOT_ID_XAX, GImPlot->CurrentPlot->XAxis.HoverRect);
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
+    if (plt == NULL) 
+        return false;
+    return BeginDragDropTargetEx(IMPLOT_ID_XAX, plt->XAxis.HoverRect);
 }
 
 bool BeginDragDropTargetY(ImPlotYAxis axis) {
-    return BeginDragDropTargetEx(IMPLOT_ID_YAX + axis, GImPlot->CurrentPlot->YAxis[axis].HoverRect);
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
+    if (plt == NULL) 
+        return false;
+    return BeginDragDropTargetEx(IMPLOT_ID_YAX + axis, plt->YAxis[axis].HoverRect);
 }
 
 bool BeginDragDropTargetLegend() {
-    return !ImHasFlag(GImPlot->CurrentPlot->Flags,ImPlotFlags_NoLegend) &&
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
-            BeginDragDropTargetEx(IMPLOT_ID_LEG, GImPlot->CurrentPlot->LegendRect);
+    if (plt == NULL) 
+        return false;
+    return !ImHasFlag(plt->Flags,ImPlotFlags_NoLegend) && BeginDragDropTargetEx(IMPLOT_ID_LEG, plt->LegendRect);
 }
 
 void EndDragDropTarget() {
@@ -2994,37 +3010,47 @@ bool BeginDragDropSourceEx(ImGuiID source_id, bool is_hovered, ImGuiDragDropFlag
 }
 
 bool BeginDragDropSource(ImGuiKeyModFlags key_mods, ImGuiDragDropFlags flags) {
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
+    if (plt == NULL) 
+        return false;
     if (ImGui::GetIO().KeyMods == key_mods) {
-        GImPlot->CurrentPlot->XAxis.Dragging = false;
+        plt->XAxis.Dragging = false;
         for (int i = 0; i < IMPLOT_Y_AXES; ++i)
-            GImPlot->CurrentPlot->YAxis[i].Dragging = false;
+            plt->YAxis[i].Dragging = false;
     }
     const ImGuiID ID = GImGui->CurrentWindow->GetID(IMPLOT_ID_PLT);
-    ImRect rect = GImPlot->CurrentPlot->PlotRect;
+    ImRect rect = plt->PlotRect;
-    return  ImGui::ItemAdd(rect, ID, &rect) && BeginDragDropSourceEx(ID, GImPlot->CurrentPlot->PlotHovered, flags, key_mods);
+    return  ImGui::ItemAdd(rect, ID, &rect) && BeginDragDropSourceEx(ID, plt->PlotHovered, flags, key_mods);
 }
 
 bool BeginDragDropSourceX(ImGuiKeyModFlags key_mods, ImGuiDragDropFlags flags) {
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
+    if (plt == NULL) 
+        return false;
     if (ImGui::GetIO().KeyMods == key_mods)
-        GImPlot->CurrentPlot->XAxis.Dragging = false;
+        plt->XAxis.Dragging = false;
     const ImGuiID ID = GImGui->CurrentWindow->GetID(IMPLOT_ID_XAX);
-    ImRect rect = GImPlot->CurrentPlot->XAxis.HoverRect;
+    ImRect rect = plt->XAxis.HoverRect;
-    return  ImGui::ItemAdd(rect, ID, &rect) && BeginDragDropSourceEx(ID, GImPlot->CurrentPlot->XAxis.ExtHovered, flags, key_mods);
+    return  ImGui::ItemAdd(rect, ID, &rect) && BeginDragDropSourceEx(ID, plt->XAxis.ExtHovered, flags, key_mods);
 }
 
 bool BeginDragDropSourceY(ImPlotYAxis axis, ImGuiKeyModFlags key_mods, ImGuiDragDropFlags flags) {
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
+    if (plt == NULL) 
+        return false;
     if (ImGui::GetIO().KeyMods == key_mods)
-        GImPlot->CurrentPlot->YAxis[axis].Dragging = false;
+        plt->YAxis[axis].Dragging = false;
     const ImGuiID ID = GImGui->CurrentWindow->GetID(IMPLOT_ID_YAX + axis);
-    ImRect rect = GImPlot->CurrentPlot->YAxis[axis].HoverRect;
+    ImRect rect = plt->YAxis[axis].HoverRect;
-    return  ImGui::ItemAdd(rect, ID, &rect) && BeginDragDropSourceEx(ID, GImPlot->CurrentPlot->YAxis[axis].ExtHovered, flags, key_mods);
+    return  ImGui::ItemAdd(rect, ID, &rect) && BeginDragDropSourceEx(ID, plt->YAxis[axis].ExtHovered, flags, key_mods);
 }
 
 bool BeginDragDropSourceItem(const char* label_id, ImGuiDragDropFlags flags) {
-    ImPlotContext& gp = *GImPlot;
+    ImPlotPlot* plt = GetCurrentOrPreviousPlot();
-    IM_ASSERT_USER_ERROR(gp.CurrentPlot != NULL, "BeginDragDropSourceItem() needs to be called between BeginPlot() and EndPlot()!");
+    if (plt == NULL) 
+        return false;
     ImGuiID source_id = ImGui::GetID(label_id);
-    ImPlotItem* item = gp.CurrentPlot->Items.GetByKey(source_id);
+    ImPlotItem* item = plt->Items.GetByKey(source_id);
     bool is_hovered = item && item->LegendHovered;
     return BeginDragDropSourceEx(source_id, is_hovered, flags, ImGuiKeyModFlags_None);
 }

implot_demo.cpp

@@ -1089,48 +1089,52 @@ void ShowDemoWindow(bool* p_open) {
                 ImPlot::SetNextLineStyle(mixed);
                 ImPlot::PlotLine("##dndxy", &dndx->Data[0].y, &dndy->Data[0].y, dndx->Data.size(), 0, 2 * sizeof(float));
             }
-            // allow the x-axis to be a DND target
-            if (ImPlot::BeginDragDropTargetX()) {
-                if (const ImGuiPayload* payload = ImGui::AcceptDragDropPayload("MY_DND")) {
-                    int i = *(int*)payload->Data; dndx = &dnd[i];
-                }
-                ImPlot::EndDragDropTarget();
-            }
-            // allow the x-axis to be a DND source
-            if (dndx != NULL && ImPlot::BeginDragDropSourceX()) {
-                ImGui::SetDragDropPayload("MY_DND", &dndx->Idx, sizeof(int));
-                ImPlot::ItemIcon(dndx->Color); ImGui::SameLine();
-                ImGui::TextUnformatted(dndx->Label);
-                ImPlot::EndDragDropSource();
-            }
-            // allow the y-axis to be a DND target
-            if (ImPlot::BeginDragDropTargetY()) {
-                if (const ImGuiPayload* payload = ImGui::AcceptDragDropPayload("MY_DND")) {
-                    int i = *(int*)payload->Data; dndy = &dnd[i];
-                }
-                ImPlot::EndDragDropTarget();
-            }
-            // allow the y-axis to be a DND source
-            if (dndy != NULL && ImPlot::BeginDragDropSourceY()) {
-                ImGui::SetDragDropPayload("MY_DND", &dndy->Idx, sizeof(int));
-                ImPlot::ItemIcon(dndy->Color); ImGui::SameLine();
-                ImGui::TextUnformatted(dndy->Label);
-                ImPlot::EndDragDropSource();
-            }
-            // allow the plot area to be a DND target
-            if (ImPlot::BeginDragDropTarget()) {
-                if (const ImGuiPayload* payload = ImGui::AcceptDragDropPayload("MY_DND")) {
-                    int i = *(int*)payload->Data; dndx = dndy = &dnd[i];
-                }
-            }
-            // allow the plot area to be a DND source
-            if (ImPlot::BeginDragDropSource()) {
-                ImGui::TextUnformatted("Yes, you can\ndrag this!");
-                ImPlot::EndDragDropSource();
-            }
             ImPlot::EndPlot();
         }
         ImPlot::PopStyleColor(2);
+
+        // you can also add DND after EndPlot:
+
+        // allow the x-axis to be a DND target
+        if (ImPlot::BeginDragDropTargetX()) {
+            if (const ImGuiPayload* payload = ImGui::AcceptDragDropPayload("MY_DND")) {
+                int i = *(int*)payload->Data; dndx = &dnd[i];
+            }
+            ImPlot::EndDragDropTarget();
+        }
+        // allow the x-axis to be a DND source
+        if (dndx != NULL && ImPlot::BeginDragDropSourceX()) {
+            ImGui::SetDragDropPayload("MY_DND", &dndx->Idx, sizeof(int));
+            ImPlot::ItemIcon(dndx->Color); ImGui::SameLine();
+            ImGui::TextUnformatted(dndx->Label);
+            ImPlot::EndDragDropSource();
+        }
+        // allow the y-axis to be a DND target
+        if (ImPlot::BeginDragDropTargetY()) {
+            if (const ImGuiPayload* payload = ImGui::AcceptDragDropPayload("MY_DND")) {
+                int i = *(int*)payload->Data; dndy = &dnd[i];
+            }
+            ImPlot::EndDragDropTarget();
+        }
+        // allow the y-axis to be a DND source
+        if (dndy != NULL && ImPlot::BeginDragDropSourceY()) {
+            ImGui::SetDragDropPayload("MY_DND", &dndy->Idx, sizeof(int));
+            ImPlot::ItemIcon(dndy->Color); ImGui::SameLine();
+            ImGui::TextUnformatted(dndy->Label);
+            ImPlot::EndDragDropSource();
+        }
+        // allow the plot area to be a DND target
+        if (ImPlot::BeginDragDropTarget()) {
+            if (const ImGuiPayload* payload = ImGui::AcceptDragDropPayload("MY_DND")) {
+                int i = *(int*)payload->Data; dndx = dndy = &dnd[i];
+            }
+        }
+        // allow the plot area to be a DND source
+        if (ImPlot::BeginDragDropSource()) {
+            ImGui::TextUnformatted("Yes, you can\ndrag this!");
+            ImPlot::EndDragDropSource();
+        }
+
         ImGui::EndChild();
     }
     //-------------------------------------------------------------------------

implot_internal.h

@@ -658,11 +658,12 @@ struct ImPlotNextItemData {
     }
 };
 
-// Holds state information that must persist between calls to BeginPlot()/EndPlot()
+// Holds transient state information that must persist between calls to BeginPlot()/EndPlot()
 struct ImPlotContext {
     // Plot States
     ImPool<ImPlotPlot> Plots;
     ImPlotPlot*        CurrentPlot;
+    ImPlotPlot*        PreviousPlot;
     ImPlotItem*        CurrentItem;
     ImPlotItem*        PreviousItem;
 
@@ -748,6 +749,8 @@ IMPLOT_API ImPlotInputMap& GetInputMap();
 IMPLOT_API ImPlotPlot* GetPlot(const char* title);
 // Gets the current plot from the current ImPlotContext
 IMPLOT_API ImPlotPlot* GetCurrentPlot();
+// Gets the current or previous plot from the current ImPlotContext
+IMPLOT_API ImPlotPlot* GetCurrentOrPreviousPlot();
 // Busts the cache for every plot in the current context
 IMPLOT_API void BustPlotCache();