From 1b4a2049a77f5b3b0688d6f9536f3614e44b7c4c Mon Sep 17 00:00:00 2001
From: epezent <epezent@rice.edu>
Date: Mon, 24 Aug 2020 08:51:03 -0500
Subject: [PATCH] fix vertical text scaling and offset

---
 implot.cpp        | 49 +++++++++++++++++++++++++++++++----------------
 implot_demo.cpp   |  2 +-
 implot_internal.h |  2 +-
 implot_items.cpp  |  2 +-
 4 files changed, 35 insertions(+), 20 deletions(-)

diff --git a/implot.cpp b/implot.cpp
index b6d738d..8962b69 100644
--- a/implot.cpp
+++ b/implot.cpp
@@ -252,22 +252,37 @@ static const ImPlotStyleVarInfo* GetPlotStyleVarInfo(ImPlotStyleVar idx) {
 // Generic Helpers
 //-----------------------------------------------------------------------------
 
-void AddTextVertical(ImDrawList *DrawList, const char *text, ImVec2 pos, ImU32 text_color) {
-    pos.x = IM_ROUND(pos.x);
-    pos.y = IM_ROUND(pos.y);
-    ImFont* font = GImGui->Font;
-    const ImFontGlyph *glyph;
-    for (char c = *text++; c; c = *text++) {
-        glyph = font->FindGlyph(c);
-        if (!glyph)
+void AddTextVertical(ImDrawList *DrawList, ImVec2 pos, ImU32 col, const char *text_begin, const char* text_end) {
+    if (!text_end)
+        text_end = text_begin + strlen(text_begin);
+    ImGuiContext& g = *GImGui;
+    ImFont* font = g.Font;
+    pos.x = IM_FLOOR(pos.x + font->DisplayOffset.y);
+    pos.y = IM_FLOOR(pos.y + font->DisplayOffset.x);
+    const char* s = text_begin;
+    const int vtx_count = (int)(text_end - s) * 4;
+    const int idx_count = (int)(text_end - s) * 6;
+    DrawList->PrimReserve(idx_count, vtx_count);
+    const float scale = g.FontSize / font->FontSize;
+    while (s < text_end) {
+        unsigned int c = (unsigned int)*s;
+        if (c < 0x80) {
+            s += 1;
+        }
+        else {
+            s += ImTextCharFromUtf8(&c, s, text_end);
+            if (c == 0) // Malformed UTF-8?
+                break;
+        }
+        const ImFontGlyph * glyph = font->FindGlyph((ImWchar)c);
+        if (glyph == NULL)
             continue;
-        DrawList->PrimReserve(6, 4);
-        DrawList->PrimQuadUV(
-            pos + ImVec2(glyph->Y0, -glyph->X0), pos + ImVec2(glyph->Y0, -glyph->X1),
-            pos + ImVec2(glyph->Y1, -glyph->X1), pos + ImVec2(glyph->Y1, -glyph->X0),
-            ImVec2(glyph->U0, glyph->V0), ImVec2(glyph->U1, glyph->V0),
-            ImVec2(glyph->U1, glyph->V1), ImVec2(glyph->U0, glyph->V1), text_color);
-        pos.y -= glyph->AdvanceX;
+        DrawList->PrimQuadUV(pos + ImVec2(glyph->Y0, -glyph->X0) * scale, pos + ImVec2(glyph->Y0, -glyph->X1) * scale,
+                             pos + ImVec2(glyph->Y1, -glyph->X1) * scale, pos + ImVec2(glyph->Y1, -glyph->X0) * scale,
+                             ImVec2(glyph->U0, glyph->V0), ImVec2(glyph->U1, glyph->V0),
+                             ImVec2(glyph->U1, glyph->V1), ImVec2(glyph->U0, glyph->V1),
+                             col);
+        pos.y -= glyph->AdvanceX * scale;
     }
 }
 
@@ -1222,8 +1237,8 @@ bool BeginPlot(const char* title, const char* x_label, const char* y_label, cons
     if (y_label) {
         const ImVec2 yLabel_size = CalcTextSizeVertical(y_label);
         const ImVec2 yLabel_pos(gp.BB_Canvas.Min.x, gp.BB_Plot.GetCenter().y + yLabel_size.y * 0.5f);
-        AddTextVertical(&DrawList, y_label, yLabel_pos, gp.Col_Y[0].MajTxt);
-    }
+        AddTextVertical(&DrawList, yLabel_pos, gp.Col_Y[0].MajTxt, y_label);
+   }
 
     // render tick labels
     ImGui::PushClipRect(gp.BB_Frame.Min, gp.BB_Frame.Max, true);
diff --git a/implot_demo.cpp b/implot_demo.cpp
index ae4ffac..9627772 100644
--- a/implot_demo.cpp
+++ b/implot_demo.cpp
@@ -548,7 +548,7 @@ void ShowDemoWindow(bool* p_open) {
             ImPlot::PlotText("Filled Markers", 2.5f, 6.0f);
             ImPlot::PlotText("Open Markers",   7.5f, 6.0f);
 
-            ImGui::PushStyleColor(ImGuiCol_Text, ImVec4(0,1,0,1));
+            ImGui::PushStyleColor(ImGuiCol_Text, ImVec4(1,0,1,1));
             ImPlot::PlotText("Fancy Markers", 5.0f, 6.0f, true);
             ImGui::PopStyleColor();
 
diff --git a/implot_internal.h b/implot_internal.h
index f4c4237..db71914 100644
--- a/implot_internal.h
+++ b/implot_internal.h
@@ -457,7 +457,7 @@ double NiceNum(double x, bool round);
 // Updates axis ticks, lins, and label colors
 void UpdateAxisColors(int axis_flag, ImPlotAxisColor* col);
 // Draws vertical text. The position is the bottom left of the text rect.
-void AddTextVertical(ImDrawList *DrawList, const char *text, ImVec2 pos, ImU32 text_color);
+void AddTextVertical(ImDrawList *DrawList, ImVec2 pos, ImU32 col, const char* text_begin, const char* text_end = NULL);
 // Calculates the size of vertical text
 ImVec2 CalcTextSizeVertical(const char *text);
 // Returns white or black text given background color
diff --git a/implot_items.cpp b/implot_items.cpp
index b593504..52ac0e0 100644
--- a/implot_items.cpp
+++ b/implot_items.cpp
@@ -1470,7 +1470,7 @@ void PlotText(const char* text, double x, double y, bool vertical, const ImVec2&
     if (vertical) {
         ImVec2 ctr = CalcTextSizeVertical(text) * 0.5f;
         ImVec2 pos = PlotToPixels(ImPlotPoint(x,y)) + ImVec2(-ctr.x, ctr.y) + pixel_offset;
-        AddTextVertical(&DrawList, text, pos, colTxt);
+        AddTextVertical(&DrawList, pos, colTxt, text);
     }
     else {
         ImVec2 pos = PlotToPixels(ImPlotPoint(x,y)) - ImGui::CalcTextSize(text) * 0.5f + pixel_offset;