From 6297c4ce521b1d308cc199c5e97013baf15f90ce Mon Sep 17 00:00:00 2001
From: Eknous-P <ehovakimyan053@gmail.com>
Date: Mon, 27 Oct 2025 20:52:01 +0400
Subject: [PATCH] groove calculator

---
 src/gui/gui.cpp   |  3 ++-
 src/gui/gui.h     |  2 ++
 src/gui/speed.cpp | 34 +++++++++++++++++++++++++++++++++-
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 6a726d4fe..797b94cdd 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -9121,7 +9121,8 @@ FurnaceGUI::FurnaceGUI():
   romMultiFile(false),
   romExportSave(false),
   pendingExport(NULL),
-  romExportExists(false) {
+  romExportExists(false),
+  desBpm(150.0) {
   // value keys
   valueKeys[SDLK_0]=0;
   valueKeys[SDLK_1]=1;
diff --git a/src/gui/gui.h b/src/gui/gui.h
index 6aaaf741e..db558b4c5 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -2835,6 +2835,8 @@ class FurnaceGUI {
 
   std::vector<String> randomDemoSong;
 
+  double desBpm;
+
   void commandExportOptions();
   
   void drawExportAudio(bool onWindow=false);
diff --git a/src/gui/speed.cpp b/src/gui/speed.cpp
index 02e04481a..56d6871d3 100644
--- a/src/gui/speed.cpp
+++ b/src/gui/speed.cpp
@@ -21,6 +21,7 @@
 #include "imgui.h"
 #include "misc/cpp/imgui_stdlib.h"
 #include "intConst.h"
+#include "IconsFontAwesome4.h"
 
 void FurnaceGUI::drawSpeed(bool asChild) {
   if (nextWindow==GUI_WINDOW_SPEED) {
@@ -49,7 +50,7 @@ void FurnaceGUI::drawSpeed(bool asChild) {
         }
       }
       ImGui::TableNextColumn();
-      float avail=ImGui::GetContentRegionAvail().x;
+      float avail=ImGui::GetContentRegionAvail().x-ImGui::GetStyle().ItemSpacing.x*2-ImGui::GetFontSize();
       float halfAvail=(avail-ImGui::GetStyle().ItemSpacing.x)*0.5;
       ImGui::SetNextItemWidth(halfAvail);
       float setHz=tempoView?e->curSubSong->hz*2.5:e->curSubSong->hz;
@@ -161,6 +162,37 @@ void FurnaceGUI::drawSpeed(bool asChild) {
           }
         }
       }
+      ImGui::SameLine();
+      ImGui::Button(ICON_FA_CALCULATOR "##grooveCalc");
+      if (ImGui::BeginPopupContextItem("##grooveCalc", ImGuiPopupFlags_MouseButtonLeft)) {
+        ImGui::InputDouble("Desired BPM", &desBpm);
+        if (ImGui::Button("OK")) {;
+          e->lockEngine([this]() {
+            unsigned char* out=e->curSubSong->speeds.val;
+            memset(out, 0, 16*sizeof(char));
+            double calcBpm=0, tickTrack=0;
+            int len=0;
+            while (len<16) {
+              if (fabs(desBpm-calcBpm)<2.2204460492503130808472633361816e-12) break;
+              double noteTime=(1.0/(desBpm/60.0))/e->curSubSong->hilightA;
+              double noteTick=noteTime*e->curSubSong->hz;
+              tickTrack+=noteTick;
+              int totalNum=0;
+              for (int i=0; i<len; i++) totalNum+=out[i];
+              out[len++]=round(tickTrack)-totalNum;
+              totalNum+=out[len-1];
+              calcBpm=60.0/((((double)totalNum/len)/e->curSubSong->hz)*e->curSubSong->hilightA);
+            }
+            e->curSubSong->speeds.len=len;
+          });
+          if (e->isPlaying()) play();
+          MARK_MODIFIED;
+          ImGui::CloseCurrentPopup();
+        }
+        ImGui::EndPopup();
+      }
+      avail=ImGui::GetContentRegionAvail().x;
+      halfAvail=(avail-ImGui::GetStyle().ItemSpacing.x)*0.5;
 
       ImGui::TableNextRow();
       ImGui::TableNextColumn();