ColorPicker / ColorEdit: restore Hue when zeroing Saturation. (#2722, #2770) - changelog, fixed uninitialized variables, tweaks, renaming.

docs/CHANGELOG.txt

@@ -35,10 +35,12 @@ HOW TO UPDATE?
 
 Other Changes:
 - Nav, Scrolling: Added support for Home/End key. (#787)
+- ColorEdit: Disable Hue edit when Saturation==0 instead of letting Hue values jump around.
+- ColorEdit, ColorPicker: In HSV display of a RGB stored value, attempt to locally preserve Hue
+  when Saturation==0, which reduces accidentally lossy interactions. (#2722, 2770) [@rokups]
 - ColorPicker: Made rendering aware of global style alpha of the picker can be faded out. (#2711)
   Note that some elements won't accurately fade down with the same intensity, and the color wheel
   when enabled will have small overlap glitches with (style.Alpha < 1.0).
-- ColorEdit: Disable Hue edit when Saturation==0 instead of letting Hue values jump around.
 - TabBar: fixed ScrollToBar request creating bouncing loop when tab is larger than available space.
 - TabBar: fixed single-tab not shrinking their width down.
 - TabBar: feed desired width (sum of unclipped tabs width) into layout system to allow for auto-resize. (#2768)

imgui_internal.h

@@ -1013,7 +1013,7 @@ struct ImGuiContext
     ImGuiID                 TempInputTextId;                    // Temporary text input when CTRL+clicking on a slider, etc.
     ImGuiColorEditFlags     ColorEditOptions;                   // Store user options for color edit widgets
     float                   ColorEditLastHue;
-    float                   ColorEditLastActiveColor[3];
+    float                   ColorEditLastColor[3];
     ImVec4                  ColorPickerRef;
     bool                    DragCurrentAccumDirty;
     float                   DragCurrentAccum;                   // Accumulator for dragging modification. Always high-precision, not rounded by end-user precision settings
@@ -1158,6 +1158,8 @@ struct ImGuiContext
         LastValidMousePos = ImVec2(0.0f, 0.0f);
         TempInputTextId = 0;
         ColorEditOptions = ImGuiColorEditFlags__OptionsDefault;
+        ColorEditLastHue = 0.0f;
+        ColorEditLastColor[0] = ColorEditLastColor[1] = ColorEditLastColor[2] = FLT_MAX;
         DragCurrentAccumDirty = false;
         DragCurrentAccum = 0.0f;
         DragSpeedDefaultRatio = 1.0f / 100.0f;

imgui_widgets.cpp

@@ -4201,9 +4201,9 @@ bool ImGui::ColorEdit4(const char* label, float col[4], ImGuiColorEditFlags flag
         ColorConvertHSVtoRGB(f[0], f[1], f[2], f[0], f[1], f[2]);
     else if ((flags & ImGuiColorEditFlags_InputRGB) && (flags & ImGuiColorEditFlags_DisplayHSV))
     {
-        ColorConvertRGBtoHSV(f[0], f[1], f[2], f[0], f[1], f[2]);
         // Hue is lost when converting from greyscale rgb (saturation=0). Restore it.
-        if (f[1] == 0 && memcmp(g.ColorEditLastActiveColor, col, sizeof(float) * 3) == 0)
+        ColorConvertRGBtoHSV(f[0], f[1], f[2], f[0], f[1], f[2]);
+        if (f[1] == 0 && memcmp(g.ColorEditLastColor, col, sizeof(float) * 3) == 0)
             f[0] = g.ColorEditLastHue;
     }
     int i[4] = { IM_F32_TO_INT8_UNBOUND(f[0]), IM_F32_TO_INT8_UNBOUND(f[1]), IM_F32_TO_INT8_UNBOUND(f[2]), IM_F32_TO_INT8_UNBOUND(f[3]) };
@@ -4335,7 +4335,7 @@ bool ImGui::ColorEdit4(const char* label, float col[4], ImGuiColorEditFlags flag
         {
             g.ColorEditLastHue = f[0];
             ColorConvertHSVtoRGB(f[0], f[1], f[2], f[0], f[1], f[2]);
-            memcpy(g.ColorEditLastActiveColor, f, sizeof(float) * 3);
+            memcpy(g.ColorEditLastColor, f, sizeof(float) * 3);
         }
         if ((flags & ImGuiColorEditFlags_DisplayRGB) && (flags & ImGuiColorEditFlags_InputHSV))
             ColorConvertRGBtoHSV(f[0], f[1], f[2], f[0], f[1], f[2]);
@@ -4514,13 +4514,15 @@ bool ImGui::ColorPicker4(const char* label, float col[4], ImGuiColorEditFlags fl
     float R = col[0], G = col[1], B = col[2];
     if (flags & ImGuiColorEditFlags_InputRGB)
     {
-        ColorConvertRGBtoHSV(R, G, B, H, S, V);
         // Hue is lost when converting from greyscale rgb (saturation=0). Restore it.
-        if (S == 0 && memcmp(g.ColorEditLastActiveColor, col, sizeof(float) * 3) == 0)
+        ColorConvertRGBtoHSV(R, G, B, H, S, V);
+        if (S == 0 && memcmp(g.ColorEditLastColor, col, sizeof(float) * 3) == 0)
             H = g.ColorEditLastHue;
     }
     else if (flags & ImGuiColorEditFlags_InputHSV)
+    {
         ColorConvertHSVtoRGB(H, S, V, R, G, B);
+    }
 
     bool value_changed = false, value_changed_h = false, value_changed_sv = false;
 
@@ -4643,7 +4645,7 @@ bool ImGui::ColorPicker4(const char* label, float col[4], ImGuiColorEditFlags fl
         {
             ColorConvertHSVtoRGB(H >= 1.0f ? H - 10 * 1e-6f : H, S > 0.0f ? S : 10*1e-6f, V > 0.0f ? V : 1e-6f, col[0], col[1], col[2]);
             g.ColorEditLastHue = H;
-            memcpy(g.ColorEditLastActiveColor, col, sizeof(float) * 3);
+            memcpy(g.ColorEditLastColor, col, sizeof(float) * 3);
         }
         else if (flags & ImGuiColorEditFlags_InputHSV)
         {
@@ -4696,9 +4698,9 @@ bool ImGui::ColorPicker4(const char* label, float col[4], ImGuiColorEditFlags fl
             R = col[0];
             G = col[1];
             B = col[2];
-            float preserve_hue = H;
             ColorConvertRGBtoHSV(R, G, B, H, S, V);
-            H = preserve_hue;                           // Avoids picker losing hue value for 1 frame glitch.
+            if (S == 0 && memcmp(g.ColorEditLastColor, col, sizeof(float) * 3) == 0) // Fix local Hue as display below will use it immediately.
+                H = g.ColorEditLastHue;
         }
         else if (flags & ImGuiColorEditFlags_InputHSV)
         {