Slider: Fixed to reach maximum value with inverted integer min/max ranges, both with signed and unsigned types. Added reverse Sliders to Demo. (#3432, #3449)

imgui_demo.cpp

@@ -617,7 +617,7 @@ static void ShowDemoWindowWidgets()
                 "Hold SHIFT/ALT for faster/slower edit.\n"
                 "Double-click or CTRL+click to input value.");
 
-            ImGui::DragInt("drag int 0..100", &i2, 1, 0, 100, "%d%%");
+            ImGui::DragInt("drag int 0..100", &i2, 1, 0, 100, "%d%%", ImGuiSliderFlags_ClampOnInput);
 
             static float f1 = 1.00f, f2 = 0.0067f;
             ImGui::DragFloat("drag float", &f1, 0.005f);
@@ -1688,6 +1688,14 @@ static void ShowDemoWindowWidgets()
         ImGui::SliderScalar("slider double low log",ImGuiDataType_Double, &f64_v, &f64_zero, &f64_one,  "%.10f", ImGuiSliderFlags_Logarithmic);
         ImGui::SliderScalar("slider double high",   ImGuiDataType_Double, &f64_v, &f64_lo_a, &f64_hi_a, "%e grams");
 
+        ImGui::Text("Sliders (reverse)");
+        ImGui::SliderScalar("slider s8 reverse",    ImGuiDataType_S8,   &s8_v,  &s8_max,    &s8_min, "%d");
+        ImGui::SliderScalar("slider u8 reverse",    ImGuiDataType_U8,   &u8_v,  &u8_max,    &u8_min, "%u");
+        ImGui::SliderScalar("slider s32 reverse",   ImGuiDataType_S32,  &s32_v, &s32_fifty, &s32_zero, "%d");
+        ImGui::SliderScalar("slider u32 reverse",   ImGuiDataType_U32,  &u32_v, &u32_fifty, &u32_zero, "%u");
+        ImGui::SliderScalar("slider s64 reverse",   ImGuiDataType_S64,  &s64_v, &s64_fifty, &s64_zero, "%I64d");
+        ImGui::SliderScalar("slider u64 reverse",   ImGuiDataType_U64,  &u64_v, &u64_fifty, &u64_zero, "%I64u ms");
+
         static bool inputs_step = true;
         ImGui::Text("Inputs");
         ImGui::Checkbox("Show step buttons", &inputs_step);

imgui_internal.h

@@ -1997,8 +1997,8 @@ namespace ImGui
     // Template functions are instantiated in imgui_widgets.cpp for a finite number of types.
     // To use them externally (for custom widget) you may need an "extern template" statement in your code in order to link to existing instances and silence Clang warnings (see #2036).
     // e.g. " extern template IMGUI_API float RoundScalarWithFormatT<float, float>(const char* format, ImGuiDataType data_type, float v); "
-    template<typename T, typename FLOAT_T>                      IMGUI_API float ScaleRatioFromValueT(ImGuiDataType data_type, T v, T v_min, T v_max, bool is_logarithmic, float logarithmic_zero_epsilon, float zero_deadzone_size);
-    template<typename T, typename FLOAT_T>                      IMGUI_API T     ScaleValueFromRatioT(ImGuiDataType data_type, float t, T v_min, T v_max, bool is_logarithmic, float logarithmic_zero_epsilon, float zero_deadzone_size);
+    template<typename T, typename SIGNED_T, typename FLOAT_T>   IMGUI_API float ScaleRatioFromValueT(ImGuiDataType data_type, T v, T v_min, T v_max, bool is_logarithmic, float logarithmic_zero_epsilon, float zero_deadzone_size);
+    template<typename T, typename SIGNED_T, typename FLOAT_T>   IMGUI_API T     ScaleValueFromRatioT(ImGuiDataType data_type, float t, T v_min, T v_max, bool is_logarithmic, float logarithmic_zero_epsilon, float zero_deadzone_size);
     template<typename T, typename SIGNED_T, typename FLOAT_T>   IMGUI_API bool  DragBehaviorT(ImGuiDataType data_type, T* v, float v_speed, T v_min, T v_max, const char* format, ImGuiSliderFlags flags);
     template<typename T, typename SIGNED_T, typename FLOAT_T>   IMGUI_API bool  SliderBehaviorT(const ImRect& bb, ImGuiID id, ImGuiDataType data_type, T* v, T v_min, T v_max, const char* format, ImGuiSliderFlags flags, ImRect* out_grab_bb);
     template<typename T, typename SIGNED_T>                     IMGUI_API T     RoundScalarWithFormatT(const char* format, ImGuiDataType data_type, T v);

imgui_widgets.cpp

@@ -2094,9 +2094,9 @@ bool ImGui::DragBehaviorT(ImGuiDataType data_type, TYPE* v, float v_speed, const
         logarithmic_zero_epsilon = ImPow(0.1f, (float)decimal_precision);
 
         // Convert to parametric space, apply delta, convert back
-        float v_old_parametric = ScaleRatioFromValueT<TYPE, FLOATTYPE>(data_type, v_cur, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+        float v_old_parametric = ScaleRatioFromValueT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, v_cur, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
         float v_new_parametric = v_old_parametric + g.DragCurrentAccum;
-        v_cur = ScaleValueFromRatioT<TYPE, FLOATTYPE>(data_type, v_new_parametric, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+        v_cur = ScaleValueFromRatioT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, v_new_parametric, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
         v_old_ref_for_accum_remainder = v_old_parametric;
     }
     else
@@ -2113,7 +2113,7 @@ bool ImGui::DragBehaviorT(ImGuiDataType data_type, TYPE* v, float v_speed, const
     if (is_logarithmic)
     {
         // Convert to parametric space, apply delta, convert back
-        float v_new_parametric = ScaleRatioFromValueT<TYPE, FLOATTYPE>(data_type, v_cur, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+        float v_new_parametric = ScaleRatioFromValueT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, v_cur, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
         g.DragCurrentAccum -= (float)(v_new_parametric - v_old_ref_for_accum_remainder);
     }
     else
@@ -2449,7 +2449,7 @@ bool ImGui::DragScalarN(const char* label, ImGuiDataType data_type, void* p_data
 //-------------------------------------------------------------------------
 
 // Convert a value v in the output space of a slider into a parametric position on the slider itself (the logical opposite of ScaleValueFromRatioT)
-template<typename TYPE, typename FLOATTYPE>
+template<typename TYPE, typename SIGNEDTYPE, typename FLOATTYPE>
 float ImGui::ScaleRatioFromValueT(ImGuiDataType data_type, TYPE v, TYPE v_min, TYPE v_max, bool is_logarithmic, float logarithmic_zero_epsilon, float zero_deadzone_halfsize)
 {
     if (v_min == v_max)
@@ -2501,11 +2501,11 @@ float ImGui::ScaleRatioFromValueT(ImGuiDataType data_type, TYPE v, TYPE v_min, T
     }
 
     // Linear slider
-    return (float)((FLOATTYPE)(v_clamped - v_min) / (FLOATTYPE)(v_max - v_min));
+    return (float)((FLOATTYPE)(SIGNEDTYPE)(v_clamped - v_min) / (FLOATTYPE)(SIGNEDTYPE)(v_max - v_min));
 }
 
 // Convert a parametric position on a slider into a value v in the output space (the logical opposite of ScaleRatioFromValueT)
-template<typename TYPE, typename FLOATTYPE>
+template<typename TYPE, typename SIGNEDTYPE, typename FLOATTYPE>
 TYPE ImGui::ScaleValueFromRatioT(ImGuiDataType data_type, float t, TYPE v_min, TYPE v_max, bool is_logarithmic, float logarithmic_zero_epsilon, float zero_deadzone_halfsize)
 {
     if (v_min == v_max)
@@ -2564,15 +2564,19 @@ TYPE ImGui::ScaleValueFromRatioT(ImGuiDataType data_type, float t, TYPE v_min, T
         }
         else
         {
-            // For integer values we want the clicking position to match the grab box so we round above
-            // This code is carefully tuned to work with large values (e.g. high ranges of U64) while preserving this property..
-            FLOATTYPE v_new_off_f = (v_max - v_min) * t;
-            TYPE v_new_off_floor = (TYPE)(v_new_off_f);
-            TYPE v_new_off_round = (TYPE)(v_new_off_f + (FLOATTYPE)0.5);
-            if (v_new_off_floor < v_new_off_round)
-                result = v_min + v_new_off_round;
+            // - For integer values we want the clicking position to match the grab box so we round above
+            //   This code is carefully tuned to work with large values (e.g. high ranges of U64) while preserving this property..
+            // - Not doing a *1.0 multiply at the end of a range as it tends to be lossy. While absolute aiming at a large s64/u64
+            //   range is going to be imprecise anyway, with this check we at least make the edge values matches expected limits.
+            if (t < 1.0)
+            {
+                FLOATTYPE v_new_off_f = (SIGNEDTYPE)(v_max - v_min) * t;
+                result = (TYPE)((SIGNEDTYPE)v_min + (SIGNEDTYPE)(v_new_off_f + (FLOATTYPE)(v_min > v_max ? -0.5 : 0.5)));
+            }
             else
-                result = v_min + v_new_off_floor;
+            {
+                result = v_max;
+            }
         }
     }
 
@@ -2672,7 +2676,7 @@ bool ImGui::SliderBehaviorT(const ImRect& bb, ImGuiID id, ImGuiDataType data_typ
             }
             else if (g.SliderCurrentAccumDirty)
             {
-                clicked_t = ScaleRatioFromValueT<TYPE, FLOATTYPE>(data_type, *v, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+                clicked_t = ScaleRatioFromValueT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, *v, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
 
                 if ((clicked_t >= 1.0f && delta > 0.0f) || (clicked_t <= 0.0f && delta < 0.0f)) // This is to avoid applying the saturation when already past the limits
                 {
@@ -2686,10 +2690,10 @@ bool ImGui::SliderBehaviorT(const ImRect& bb, ImGuiID id, ImGuiDataType data_typ
                     clicked_t = ImSaturate(clicked_t + delta);
 
                     // Calculate what our "new" clicked_t will be, and thus how far we actually moved the slider, and subtract this from the accumulator
-                    TYPE v_new = ScaleValueFromRatioT<TYPE, FLOATTYPE>(data_type, clicked_t, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+                    TYPE v_new = ScaleValueFromRatioT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, clicked_t, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
                     if (!(flags & ImGuiSliderFlags_NoRoundToFormat))
                         v_new = RoundScalarWithFormatT<TYPE, SIGNEDTYPE>(format, data_type, v_new);
-                    float new_clicked_t = ScaleRatioFromValueT<TYPE, FLOATTYPE>(data_type, v_new, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+                    float new_clicked_t = ScaleRatioFromValueT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, v_new, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
 
                     if (delta > 0)
                         g.SliderCurrentAccum -= ImMin(new_clicked_t - old_clicked_t, delta);
@@ -2703,7 +2707,7 @@ bool ImGui::SliderBehaviorT(const ImRect& bb, ImGuiID id, ImGuiDataType data_typ
 
         if (set_new_value)
         {
-            TYPE v_new = ScaleValueFromRatioT<TYPE, FLOATTYPE>(data_type, clicked_t, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+            TYPE v_new = ScaleValueFromRatioT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, clicked_t, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
 
             // Round to user desired precision based on format string
             if (!(flags & ImGuiSliderFlags_NoRoundToFormat))
@@ -2725,7 +2729,7 @@ bool ImGui::SliderBehaviorT(const ImRect& bb, ImGuiID id, ImGuiDataType data_typ
     else
     {
         // Output grab position so it can be displayed by the caller
-        float grab_t = ScaleRatioFromValueT<TYPE, FLOATTYPE>(data_type, *v, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
+        float grab_t = ScaleRatioFromValueT<TYPE, SIGNEDTYPE, FLOATTYPE>(data_type, *v, v_min, v_max, is_logarithmic, logarithmic_zero_epsilon, zero_deadzone_halfsize);
         if (axis == ImGuiAxis_Y)
             grab_t = 1.0f - grab_t;
         const float grab_pos = ImLerp(slider_usable_pos_min, slider_usable_pos_max, grab_t);