From 942c6ea7d89a0473b4f2b5529c516316b0b44b6b Mon Sep 17 00:00:00 2001
From: Vojtech Bubnik <bubnikv@gmail.com>
Date: Mon, 20 Dec 2021 14:47:43 +0100
Subject: Follow-up to 2e250c1463c5d8e8bc94d0769e3e82d648e99e3b
 2f638058570197aa2832d0343148741ad6dbba6b The issue was caused by
 2e250c1463c5d8e8bc94d0769e3e82d648e99e3b that did not do the binning of
 floating values well for small numbers, small numbers were rounded to zero.
 The new code now rounds to two significant digits similarly to sprintf(buf,
 "%.2g", value)

---
 src/slic3r/GUI/GCodeViewer.cpp | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

(limited to 'src/slic3r/GUI')

diff --git a/src/slic3r/GUI/GCodeViewer.cpp b/src/slic3r/GUI/GCodeViewer.cpp
index 8b887bd3d..d3a2e784b 100644
--- a/src/slic3r/GUI/GCodeViewer.cpp
+++ b/src/slic3r/GUI/GCodeViewer.cpp
@@ -73,14 +73,19 @@ static std::vector<std::array<float, 4>> decode_colors(const std::vector<std::st
     return output;
 }
 
-static float round_to_nearest_percent(float value)
+// Round to a bin with minimum two digits resolution.
+// Equivalent to conversion to string with sprintf(buf, "%.2g", value) and conversion back to float, but faster.
+static float round_to_bin(const float value)
 {
-    return std::round(value * 100.f) * 0.01f;
-}
-
-static float round_to_nearest_perthousand(float value)
-{
-    return std::round(value * 1000.f) * 0.001f;
+    assert(value > 0);
+    constexpr float const scale    [5] = { 100.f,  1000.f,  10000.f,  100000.f,  1000000.f };
+    constexpr float const invscale [5] = { 0.01f,  0.001f,  0.0001f,  0.00001f,  0.000001f };
+    constexpr float const threshold[5] = { 0.095f, 0.0095f, 0.00095f, 0.000095f, 0.0000095f };
+    // Scaling factor, pointer to the tables above.
+    int                   i            = 0;
+    // While the scaling factor is not yet large enough to get two integer digits after scaling and rounding:
+    for (; value < threshold[i] && i < 4; ++ i) ;
+    return std::round(value * scale[i]) * invscale[i];
 }
 
 void GCodeViewer::VBuffer::reset()
@@ -143,7 +148,7 @@ bool GCodeViewer::Path::matches(const GCodeProcessorResult::MoveVertex& move) co
         // use rounding to reduce the number of generated paths
         return type == move.type && extruder_id == move.extruder_id && cp_color_id == move.cp_color_id && role == move.extrusion_role &&
             move.position.z() <= sub_paths.front().first.position.z() && feedrate == move.feedrate && fan_speed == move.fan_speed &&
-            height == round_to_nearest_perthousand(move.height) && width == round_to_nearest_percent(move.width) &&
+            height == round_to_bin(move.height) && width == round_to_bin(move.width) &&
             matches_percent(volumetric_rate, move.volumetric_rate(), 0.05f);
     }
     case EMoveType::Travel: {
@@ -176,7 +181,7 @@ void GCodeViewer::TBuffer::add_path(const GCodeProcessorResult::MoveVertex& move
     Path::Endpoint endpoint = { b_id, i_id, s_id, move.position };
     // use rounding to reduce the number of generated paths
     paths.push_back({ move.type, move.extrusion_role, move.delta_extruder,
-        round_to_nearest_perthousand(move.height), round_to_nearest_percent(move.width),
+        round_to_bin(move.height), round_to_bin(move.width),
         move.feedrate, move.fan_speed, move.temperature,
         move.volumetric_rate(), move.extruder_id, move.cp_color_id, { { endpoint, endpoint } } });
 }
@@ -751,12 +756,12 @@ void GCodeViewer::refresh(const GCodeProcessorResult& gcode_result, const std::v
         {
         case EMoveType::Extrude:
         {
-            m_extrusions.ranges.height.update_from(round_to_nearest_perthousand(curr.height));
-            m_extrusions.ranges.width.update_from(round_to_nearest_percent(curr.width));
+            m_extrusions.ranges.height.update_from(round_to_bin(curr.height));
+            m_extrusions.ranges.width.update_from(round_to_bin(curr.width));
             m_extrusions.ranges.fan_speed.update_from(curr.fan_speed);
             m_extrusions.ranges.temperature.update_from(curr.temperature);
             if (curr.extrusion_role != erCustom || is_visible(erCustom))
-                m_extrusions.ranges.volumetric_rate.update_from(round_to_nearest_percent(curr.volumetric_rate()));
+                m_extrusions.ranges.volumetric_rate.update_from(round_to_bin(curr.volumetric_rate()));
             [[fallthrough]];
         }
         case EMoveType::Travel:
-- 
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